Emotion regulation and coping strategies are among the most important psychological mechanisms affecting the adjustment of children with cancer during chemotherapy, as these children simultaneously face the physical pressures caused by the disease, concerns about the future, fear of medical procedures, and extensive changes in daily life. Diagnosis of cancer in childhood can affect the sense of security, independence, and predictability of the environment, and put the child in a situation where he needs specialized support to understand the experience of the disease and manage the emotions caused by it. Chemotherapy also provides the basis for the formation of a variety of emotional reactions due to its repetitive nature, the possibility of physical complications, frequent hospital visits, and the possible experience of pain and nausea. In such situations, emotion regulation refers to the child's ability to identify, understand, accept, and modulate their emotions in response to difficult situations, and plays an important role in how they deal with therapeutic situations. Emotion regulation does not mean eliminating fear, sadness, anger, or worry, but rather helps the child experience and express these emotions in a way that is appropriate to the situation, and to continue with daily activities and the treatment process without being completely affected by them. From a theoretical point of view, cognitive, behavioral, developmental, and attachment-based approaches each explain aspects of the relationship between emotion regulation and psychological adjustment in children with cancer. Based on cognitive perspectives, the child's perception of the disease, his or her interpretation of therapeutic measures, and his assessment of the degree of control over the situation affect the intensity and type of emotional reactions. A child who perceives chemotherapy as a completely uncontrollable and threatening experience may show more anxiety, while a child who receives age-appropriate information with the help of parents and the treatment team can gain a more realistic understanding of the treatment process. This difference in cognitive assessment does not necessarily mean a difference in the severity of the disease, but rather suggests that how the treatment experience is interpreted can play a role in the formation of psychological responses. On the other hand, theories of emotional development emphasize that children's ability to regulate emotion is still evolving, and that their degree of autonomy in managing fear and worry depends on age, level of cognitive development, previous experiences, and the quality of adult support. Young children may express their emotions more often through crying, restlessness, clinging to parents, resistance to therapeutic measures, or play, while older children can express their concerns in words and use more sophisticated cognitive strategies. Therefore, the evaluation of emotion regulation should be done according to the child's developmental characteristics, and not all children, regardless of their age and experience, should be expected to cope with chemotherapy in the same way. In addition to emotion regulation, coping strategies are a set of cognitive, emotional, and behavioral efforts that the child employs to manage stressful situations. These strategies can be problem-oriented, emotion-based, or avoidance-based, and their effectiveness depends on the type of situation, the intensity of the stress, the available facilities, and the child's individual characteristics. Problem-focused coping becomes important when a child is able to manage part of the situation by gaining information, participating in age-appropriate decisions, or learning practical skills. For example, gradually becoming familiar with the therapeutic environment, choosing a toy to take with you during injections, or learning to breathe slowly can increase feelings of participation and perceived control. Emotion-focused coping focuses more on reducing emotional distress and tolerating difficult emotions and may include talking to parents, receiving emotional support, using mental imagery, playing, painting, or relaxation exercises. In contrast, avoiding anxiety-inducing situations may create a sense of calm in the short term, but if it becomes the dominant role model for the child, it can limit the opportunity to learn adaptive skills and perpetuate the anxiety associated with therapeutic measures. However, any kind of temporary distancing from a stressful situation should not be considered maladaptive, as resting, shifting attention, and having fun sometimes help the child reduce the intensity of the excitement and regain his or her ability to continue the treatment process. The main issue is the child's flexibility in choosing the appropriate strategy, not the constant use of a particular method. In fact, optimal adjustment is formed when the child is able to switch between expressing emotions, solving problems, seeking support, and changing the direction of attention according to the situation. Research evidence in child health psychology and cancer psychology shows that anxiety, worry about medical procedures, sleep problems, mood symptoms, and behavioral difficulties are among the reactions that may be observed during cancer treatment, although their intensity and persistence are not the same in different children. Research on coping with chronic diseases in children also emphasizes the importance of social support, a sense of competence, constructive communication with caregivers, and the use of coping strategies appropriate to the stage of development. Studies of psychological interventions in paediatric oncology have investigated methods such as pre-action preparedness training, distractions, guided imagery, slow breathing, play therapy, and cognitive-behavioural interventions to reduce treatment-related anxiety and distress. The results of these studies generally support the capacity of such interventions to reduce some symptoms of distress, but their effectiveness varies according to the type of intervention, the child's age, treatment setting, assessment tools, and the quality of the research. Therefore, it cannot be concluded that a specific coping strategy is best for all children or at all stages of chemotherapy. Also, the relationship between emotion regulation and psychological adjustment is multidimensional and may be influenced by other factors such as the severity of physical complications, history of anxiety, quality of family relationships, peer support, and social circumstances. Children who are able to recognize their emotions and have the appropriate vocabulary to express them usually find more opportunities to seek help and use adult support. In contrast, children who are unable to accurately identify or express their emotions may express psychological distress through protest behaviors, withdrawal, aggression, or physical complaints. These behaviors should not be quickly attributed to anonymity or stubbornness, as they sometimes represent fear, feelings of powerlessness, experiencing pain, or a need for reassurance. In a therapy setting, paying attention to the emotional meaning of a child's behavior can help health workers identify the underlying causes of their discomfort rather than focusing solely on controlling the behavior. For example, a child's resistance to entering the treatment room may be caused by a previous unpleasant experience, the expectation of pain, separation from parents, or ignorance of the steps to take medical action. Identifying these factors allows for more appropriate intervention choices and prevents conflict escalation between the child and caregivers. The role of parents in shaping and strengthening emotion regulation is particularly important, as children use adult emotional reactions in many difficult situations to assess risk and security. Parents who listen to the child's concerns with relative calmness, validate their feelings, and provide clear and age-appropriate information can provide a suitable context for learning adaptive coping. Conversely, completely hiding the reality of the illness, making unreliable promises, or minimizing a child's fear may undermine their confidence and reduce the expression of difficult emotions. Of course, effective support does not mean that parents should always be calm or never show concern, but it is important to be able to manage their emotions in such a way that the child does not feel abandoned or threatened in a therapeutic situation. From this perspective, psychological interventions should also involve parents, if possible, and make emotion regulation training a common skill in the family system. The stress of cancer may reduce parents' coping resources, and their anxiety may directly or indirectly affect the child's experience. Therefore, assessing caregivers' psychological status and providing them with appropriate support is part of comprehensive child care. In addition to the family, the quality of the treatment team's relationship with the child can contribute to their sense of security and ability to cope. Honest and understandable explanation of medical procedures, allowing the child to ask questions, offering limited but realistic choices, and respecting their emotional reactions can increase the sense of involvement. Even in situations where the child is unable to change the principle of treatment, the choice of the order of certain activities, the type of hobby, or the method of receiving support can create an experience of authority tailored to the child's circumstances. This sense of authority does not mean that the child is given responsibility for medical decisions, but rather that it is a way to maintain the child's dignity, participation, and developmental independence within a safe range. In terms of clinical application, the assessment of emotion regulation and coping strategies should be done before starting chemotherapy and during the various stages of treatment, as the child's needs may change as the child's physical condition changes, increases the treatment experience, or new complications occur. Age-appropriate interviews, behavior observations, conversations with parents, and the use of valid assessment tools can provide additional information about the child's anxiety, mood, behavioral problems, and coping resources. In this assessment, it is necessary to consider the difference between the child's normal and transient response to a difficult situation with severe, persistent, or impairing distress. Not all children with cancer need intensive psychological intervention, but all deserve care that takes into account their feelings, developmental needs, and family circumstances. For children with severe anxiety, persistent fear of medical procedures, or serious problems with adjustment, a referral to a child clinical psychologist or psycho-oncologist may be necessary. Age-appropriate cognitive-behavioral interventions, coping skills training, progressive exposure training, and family support are some of the methods that can be used according to clinical evaluation. In the meantime, play and art can be valuable tools to facilitate the expression of emotion, especially when a child does not yet have the ability to verbally describe their complex experiences. Painting, storytelling, puppetry, and creative activities give a child the opportunity to express their fears, questions, and perceptions of illness in a safe environment. These activities should not be interpreted as a definitive diagnostic tool for a psychological disorder or as a substitute for a specialized assessment, but rather as part of therapeutic communication and targeted emotional support. For example, a child can use drawings to represent the stages of being in the hospital and then discuss the scary or unbearable parts of their experience with the therapist's help. Such an activity may help identify false beliefs, hidden concerns, and situations that need more support. Using age-appropriate stories can also help a child explore their emotions in the form of understandable characters and situations, and learn different ways of dealing with problems. However, the choice of these methods should be made according to the child's preferences, physical condition, energy level, and treatment conditions, and should not become a compulsive or boring activity. One of the major challenges in this area is the fluctuation in the child's physical condition during the course of chemotherapy, as fatigue, nausea, pain, changes in appetite, and sleep disturbances may reduce the child's capacity for attention and participation. In such a situation, it is not realistic to expect the continued use of complex cognitive strategies, and interventions should be short, flexible, and tailored to the child's physical ability. Another challenge is individual differences in the way emotions are experienced and expressed; some children tend to talk about illness, while others prefer to manage their emotions through play, silence, or nonverbal activities. Imposing a fixed way of expressing emotion can be counterproductive and create feelings of frustration or more pressure. Cultural and family differences also affect the meaning that children and parents place on illness, pain, dependence, and independence, and should be included in the design of interventions. In addition, time constraints in health centers, insufficient access to child mental health professionals, family economic pressure, and the difficulty of frequent commutes may make it difficult to continue psychological interventions. To alleviate these constraints, integrating psychological services into the oncology care program, early training for treatment team members, and establishing specific referral pathways can improve children's access to the support they need. The use of in-person services can also meet some of the family's support needs in appropriate circumstances, although access to technology, confidentiality, and age-appropriate intervention should be considered. Another limitation of the research is the difficulty of separating the effect of emotion regulation from simultaneous factors such as disease severity, medications taken, treatment complications, and the child's previous psychological status. Also, differences in the definition of psychological adjustment and the use of different tools in the studies make it difficult to directly compare the findings. In addition, many of the results of interventional studies depend on specific conditions and samples and should be generalized to all children with cancer with caution. In order to develop knowledge in this field, it is important to conduct longitudinal studies that examine changes in emotion regulation, coping strategies, and adjustment indicators at different stages of treatment. Also, individually assessing the experience of children at different ages, paying attention to cultural and family differences, and examining the role of peer support can help to design more accurate interventions. In addition to reducing anxiety, future research should also examine outcomes such as child participation in therapy, quality of life, sleep, academic performance, social relationships, and the level of sense of control to obtain a more comprehensive picture of adjustment. Examining the acceptance of interventions by children and parents and measuring the feasibility of implementing them in real-world therapeutic environments is also necessary to turn scientific findings into practical services. Finally, emotion regulation and coping strategies should be considered as two related and complementary processes that affect the psychological adjustment of a child with cancer in interaction with individual characteristics, family support, and the quality of medical care. Emotion regulation helps the child to recognize and manage his emotions, while coping strategies make it possible to convert this emotional capacity into actions appropriate to difficult situations. None of these processes alone guarantee optimal adjustment, and the child should not be expected to remain calm, hopeful, or fearless throughout all stages of chemotherapy. Psychological adjustment does not mean unquestioning accepting suffering or ignoring the difficulties of the disease, but rather having the resources to endure pressure, express needs, receive support, and maintain parts of life that are appropriate to the treatment situation. Accordingly, an effective approach should focus on fostering psychological resilience, a sense of security, coping skills, and the child's participation in care, rather than simply emphasizing symptom reduction. Collaboration between a psycho-oncology specialist, child psychologist, doctor, nurse, and family can pave the way for the implementation of such an approach and increase the likelihood of early identification of emotional problems. In this context, paying attention to the child's needs along with physical care is not a marginal measure, but an essential part of comprehensive treatment for childhood cancer, because mental health support can help the child go through the treatment experience with more resources, maintain supportive relationships, and follow the path of adjustment and return to meaningful life activities to the best of their ability and circumstances.