The psychological distress of family members of patients with cancer is one of the important and less neglectable consequences of the experience of the disease, which can begin at the time of diagnosis and continue at different stages of treatment, disease recurrence, survival, and palliative care. Exposure to cancer usually does not only affect the patient's physical health, but also the emotional, relational, and functional system of the family, and family members may face varying levels of anxiety, depression, helplessness, sleep disturbances, and burnout in the face of uncertainty, worry about the future, fear of death, change of roles, financial pressures, and caring responsibilities. From the perspective of the theoretical foundations of psycho-oncology, psychological distress in the family should be understood in the context of the interaction of biological, psychological, social, and spiritual factors, and it cannot be considered as a mere individual reaction and separate from the circumstances of the disease. The family systems approach shows that the illness of one member can alter the balance of the entire family system, and as a result, reducing the distress of one member may be accompanied by improved communication, support, and adaptation of other members. Accordingly, psycho-oncological interventions are designed with the aim of identifying and reducing the aggravating factors of distress, strengthening coping resources, and increasing the capacity of family adjustment. The first step in these interventions is to accurately assess psychological distress, as family members' reactions may range from normal and expected worry to clinical symptoms of anxiety, depression, stress disorder, and caregiver burnout. Using clinical interviews, observation of family interactions, and validated screening tools, the psycho-oncologist can determine the severity of distress, support resources, coping styles, relationship quality, and specific needs of each member. This assessment should be repeated throughout the course of the disease, as the severity of distress is not constant and may increase at the time of diagnosis, initiation of chemotherapy, surgery, radiation therapy, receipt of test results, or exposure to recurrence. Cognitive-behavioral interventions are one of the approaches that can be used to reduce family distress and can help reduce anxiety and feelings of helplessness by identifying catastrophic thoughts, correcting unrealistic perceptions, teaching problem-solving, and reinforcing coping strategies. In many families, thoughts such as "there's nothing we can do," "every symptom is a sign that the disease is getting worse," or "we must always be strong" can increase stress, and cognitive interventions help family members more accurately assess these thoughts and replace them with more flexible patterns. Emotion regulation training is also an important part of psycho-oncological programs, as family members may turn to emotion suppression, avoidance, irritability, or extreme care in the face of fear and anxiety. Training skills such as calming breathing, mindfulness, self-regulation, emotion tolerance, and intrusive thought management can increase the family's capacity to cope with stressful situations. Along with individual interventions, family therapy can be used to correct dysfunctional communication patterns, reduce conflict, and strengthen mutual support. Cancer sometimes causes family members to disagree about how much information should be shared with the patient, how to make treatment decisions, or the extent of the patient's limitations, and these disagreements can increase distress. By creating a safe communication environment, a psycho-oncologist can help family members express their concerns, needs, and feelings without blame or overly defensive. Another important mechanism for reducing distress is to increase a sense of control and self-efficacy, as exposure to cancer often comes with the experience of unpredictability, and family members may feel like they have lost control of their daily lives. Training in problem-solving skills, care planning, division of responsibilities, and recognition of available resources can rebuild some of this sense of control. Psychological support can also reduce ambiguity and anxiety caused by ignorance by educating caregivers about the patient's needs, potential complications of treatment, and how to respond appropriately to emotional changes; however, psychological and educational information should be provided with valid medical information and coordinated with the treatment team to avoid creating false impressions. In families where long-term care has been entrusted to an individual, attention to caregiver burnout is particularly important, as the constant strain of care can lead to reduced sleep, fatigue, social isolation, irritability, and a decrease in the caregiver's quality of life. Psycho-oncological interventions in these settings can focus on setting healthy boundaries, sharing responsibility among family members, fostering social support, and making time for self-care. Acceptance and commitment-based approaches can also help family members balance accepting the reality of illness with continuing valuable life activities, and learn a more adaptive way to deal with unpleasant emotions rather than constantly struggling with unpleasant emotions. In a situation where cancer is accompanied by a crisis of meaning and existential questions, meaning-based interventions can help the family discuss shared values, realistic hope, meaningful relationships, and the meaning of care. This process does not mean denying the severity of the illness or offering unrealistic hope, but rather aims to maintain the family's psychological and communication resources in difficult situations. Support groups can also help reduce distress by creating a sense of belonging, reducing social isolation, and allowing for the exchange of experiences with families with similar situations. In recent years, online interventions and telepsycho-oncology have also gained traction as a way to increase families' access to psychological services and can be applied to families who are unable to attend in person due to geographical distance, mobility restrictions, or a lack of specialists. However, digital interventions should be considered in terms of confidentiality, information security, quality of therapeutic communication, and equitable access. The effectiveness of psycho-oncological interventions also depends on the time of onset, distress severity, type of cancer, stage of the disease, family structure, economic status, culture, family beliefs, and level of social support, and a single intervention cannot be expected to have the same effect for all families. One of the important limitations in this area is the focus of health systems on the patient and the relative lack of attention to the psychological needs of caregivers and other family members, so family distress may be identified when it has reached a significant level. Another limitation is the lack of trained professionals in psycho-oncology and the lack of integrated protocols for screening and family intervention in some treatment centers. Also, the social stigma associated with receiving psychological services may cause some families to hide their symptoms or consider visiting a specialist as a sign of weakness. It is suggested that psychological distress screening of family members be carried out along with patient evaluation at critical points along the treatment path, and families with moderate or severe distress should be referred for intervention in a targeted manner. Designing stage-based intervention programs, using hybrid models including education, support, cognitive-behavioral and family-centered interventions, and simultaneous attention to the patient and caregiver can increase care continuity. Psycho-oncologist collaboration with the oncologist, nurse, social worker, and other members of the treatment team is also essential to coordinate information and avoid contradictory messages. Overall, psycho-oncological interventions can help to moderate psychological distress in the family and provide better adaptation to the complex course of cancer by reducing anxiety and depression, enhancing emotion regulation, increasing self-efficacy, improving family communication, reducing caregiver burnout, and strengthening social support. The ultimate goal of these interventions is not only to eliminate negative emotions, but also to create a psychological and communication capacity for flexible, conscious, and meaningful confrontation with the disease, so that the family can support the patient, as well as maintain the mental health and quality of life of its members as much as possible.