As one of the main methods of treating many childhood malignancies, chemotherapy plays an essential role in controlling the disease, reducing the likelihood of cancer progression, and increasing the chances of recovery, but the treatment process and its possible complications can affect various aspects of a child's quality of life and mental health. Psychological analysis of the consequences of chemotherapy requires simultaneous attention to physical status, cognitive function, emotion regulation, family relationships, social participation, academic achievement, and the child's perception of the future. Quality of life in children with cancer is a multidimensional concept that is not limited to the absence of physical symptoms, but also includes a sense of security, the ability to perform daily activities, satisfaction with social relationships, emotional support, and the ability to participate in age-appropriate experiences. From this perspective, the success of medical treatment and the quality of the child's lived experience are two related but distinct issues: treatment may be medically effective, while the child may still face fatigue, anxiety, activity limitations, or difficulties with psychological adjustment. Also, the severity and type of treatment outcomes are not the same in all children and depend on the type of cancer, medication regimen, duration of treatment, physical condition, age, stage of development, previous experiences, family support resources, and social conditions. From a theoretical perspective, the biological, psychological, and social model provides an appropriate framework for explaining these outcomes, as it shows that physical changes induced by illness and treatment affect quality of life through interaction with thoughts, emotions, behaviors, and the social environment. For example, treatment-induced fatigue may reduce a child's ability to play, attend school, and communicate with friends; these limitations can also increase feelings of isolation, frustration, or loss of independence. As a result, the physical and psychological consequences of chemotherapy often do not act in isolation, but rather affect each other in a reciprocal cycle. One of the most important aspects of mental health during this period is anxiety related to illness and treatment. Children may worry about pain, medication complications, hospitalization, test results, family separation, or the possibility of the disease returning. The nature of these concerns changes with the child's age and level of cognitive development; young children are more likely to express fear through crying, clinging to parents, restlessness, or refusal to cooperate, while older children and adolescents are able to express more complex concerns about the future, body image, social relationships, and personal independence. Anticipatory anxiety may also be formed by previous adverse experiences and activated before entering the treatment setting or initiating a medical procedure. If this anxiety is severe and persistent, it may affect the child's tolerance to treatment measures, sleep, appetite, and participation in daily activities. However, the presence of concern about serious illness is not necessarily a sign of a mental disorder, and the clinical evaluation should consider the severity, persistence, and extent of the impairment. Depression and symptoms associated with low mood are also important topics in assessing the mental health of children with cancer. Limitation of enjoyable activities, distance from friends, constant fatigue, physical changes, and feelings of uncertainty about the future may lead to sadness, decreased motivation, irritability, or social withdrawal. In children, symptoms of depression do not always appear in the form of overt sadness and sometimes manifest in the form of boredom, decreased interest in play, decreased interaction, or behavioral changes. On the other hand, fatigue, sleep disturbance, and decreased appetite may overlap with the physical side effects of treatment, so diagnosing mood problems requires careful medical and psychological examination. By regularly assessing emotional symptoms, reviewing sources of support, and identifying risk factors, a psycho-oncologist can help diagnose problems early and choose appropriate interventions. The impact of chemotherapy on body image and sense of identity is also particularly important, especially in children who experience changes such as hair loss, weight changes, skin changes, or other appearance complications. These changes may result in feelings of being different from peers, worry about the way others look, or decrease self-esteem. These experiences can be even more important in adolescents, as identity formation, body acceptance, and belonging to a peer group are important developmental tasks of this period. Psychological support in this regard should focus on accepting the child's feelings, strengthening the identity beyond the illness, increasing age-appropriate awareness, and providing the opportunity to make choices about how to manage changes in appearance. In this process, the child should not be expected to always have a positive attitude or not to feel anxious about changes in his or her body. Accepting unpleasant emotions and providing a safe space to express them is an important part of therapeutic support. Another dimension of the impact of chemotherapy is changes in cognitive function and educational activities. Some children may experience problems with attention, concentration, memory, information processing speed, or completing schoolwork during or after treatment. The severity and cause of these problems vary, and not all cognitive difficulties can be directly attributed to chemotherapy, as illness, fatigue, pain, sleep disturbances, psychological stress, and some associated therapies can also play a role in cognitive function. In cases where cognitive problems are persistent or significant, specialized assessment and coordination with the school and family can help identify educational needs and design appropriate supports. Flexibility in the curriculum, adjusting the volume of assignments, providing the child with the opportunity to rest, and maintaining contact with teachers and peers can reduce unnecessary stress. The purpose of these supports is not to eliminate developmental expectations, but to provide the conditions in which the child can make a meaningful contribution to learning, given the abilities and limitations of the course of treatment. Family relationships also play a pivotal role in determining a child's quality of life. A cancer diagnosis and the initiation of chemotherapy can alter the usual structure of family life, leaving parents with worries about the future, caring responsibilities, financial pressures, and difficulty coordinating between treatment and daily life. These pressures may affect family interactions and how they respond to the child's needs. At the same time, the family can be one of the most important sources of security, realistic hope, and emotional support. The quality of parental communication with the child, the level of emotional availability, age-appropriate honesty, and the ability to accept their emotions can help to cope better. Educating parents on how to talk to the child, answer difficult questions, manage their anxiety, and recognize signs of distress can be part of a comprehensive care plan. It is also important to pay attention to the needs of sick siblings, as changes in parental attention and family planning may affect children's sense of security and relationships. At the social level, staying away from peers and reducing participation in recreational activities can increase the experience of loneliness and disconnection from normal life. Regular and appropriate communication with friends, participation in favorite activities, and maintaining a connection to the educational environment can help to maintain a child's social identity if they are compatible with medical conditions. Children should not be considered disabled solely on the basis of a cancer diagnosis, but should be provided with safe and appropriate opportunities for play, learning, connection, and experience independence. In terms of research, quality of life studies of children with cancer suggest that physical condition, emotional symptoms, family relationships, and social participation should be assessed simultaneously. Proprietary childhood cancer-related quality of life tools, along with measures of anxiety, depression, pain, and fatigue, can provide a more comprehensive picture of a patient's condition. However, the child's report, parent's report, and expert evaluation may differ from each other; for example, parents may see physical limitations more prominently, while the child may be more concerned about their friendships or changes in appearance. Therefore, it is important to combine information from different sources and consider the child's own perspective. Validity, age, language, and cultural context should also be taken into account in the selection of assessment tools, and the results should be dynamically examined during treatment. Quality of life may change during different periods of chemotherapy; some symptoms become more severe in the days leading up to receiving medication and decrease in the interval between sessions, while some psychological or cognitive problems may persist. Therefore, a single assessment cannot fully show a child's adjustment path. Psychological interventions aimed at reducing distress and maintaining quality of life should be tailored to individual needs. A cognitive-behavioral approach can help identify worrying thoughts, strengthen problem-solving skills, and teach coping strategies. Practicing slow breathing, relaxation, mental imagery, and distraction may also be helpful in managing anxiety and discomfort associated with medical procedures. Play therapy and art therapy can provide opportunities to express emotion, process the experience of illness, and foster a sense of control, especially in children who find it difficult to verbally express emotions. These methods should be chosen based on the child's needs and preferences and should not replace medical evaluation, proper control of physical symptoms, or necessary specialized interventions. Psychological support for the family and coordination between the psycho-onclogist, physician, nurse, child psychiatrist if needed, social worker, and school can also help to continuate care. One of the main challenges in this area is the significant differences between children in terms of the type of disease, the severity of complications, support resources, and developmental needs, so a one-size-fits-all program is not suitable for all patients. Limited access to specialists, time pressure in health centers, difficulty in long-term follow-up, and differences in research tools may also make it difficult to evaluate and implement interventions. In addition, not all of the psychological outcomes observed during chemotherapy can be directly caused by drugs, because cancer itself, concern about the future, hospitalization, changes in social relationships, and other concomitant treatments also play a role in these outcomes. Therefore, scientific analysis should distinguish between statistical association and causal relationship and avoid generalizing the results of a limited study to all children. It is suggested that treatment centers include quality of life and mental health assessment alongside monitoring of physical indicators and design a specific program for psychological screening, referral and follow-up. It is best to start from the time of diagnosis and continue during chemotherapy, the end of treatment, and the follow-up period, as a child's psychological needs are transformed as medical conditions change and a gradual return to daily life. Developing age-appropriate support programs, educating parents, maintaining contact with school, providing opportunities for social participation, and early identification of cognitive and emotional problems can help reduce the psychological burden of treatment. Also, future research should focus on longitudinal review of quality of life, identification of protective factors, comparison of psychological interventions, and assessment of long-term outcomes of treatment to determine which methods are most effective for which groups of children, under what conditions, and with what persistence. All in all, chemotherapy, along with its vital role in cancer treatment, may create a series of physical, emotional, cognitive, and social consequences that affect a child's quality of life and mental health. Understanding these outcomes requires a holistic view that considers the child not merely the recipient of medical treatment, but also as a growing individual with emotional, social, educational, and family needs. The role of the psycho-oncologist in this framework is to identify and assess distress, promote psychological adjustment, support the family, coordinate with the treatment team, and help maintain quality of life. Optimal care is achieved when the success of treatment is not only measured by medical indicators, but also by the child's sense of security, ability to cope, social participation, and the possibility of continuing to live in accordance with the child's age. The ultimate goal is to provide conditions in which the child receives effective treatment, has adequate psychological support, and can maintain his or her developmental capacities, meaningful relationships, and realistic hope with the least preventable pressure.