The role of the psycho-oncologist in psychological support for the families of cancer patients is one of the essential components of comprehensive and patient-centered care in the cancer care system, because cancer is not just a physical illness and its consequences can affect the emotional, communication, social, and functional structure of the entire family. Cancer diagnosis often triggers a series of emotional reactions in family members, and anxiety, fear, sadness, anger, feelings of helplessness, worry about the future, and fear of losing the patient may intensify during different periods of the disease. From the perspective of theoretical foundations, the psychosocial and spiritual approach considers the family as a part of the main context of the experience of the disease, and accordingly, the patient's psychological status is not separate from the interaction with the family environment. In this framework, the psycho-oncologist tries to identify the risk factors, support resources, coping patterns, and family adaptation capacity by simultaneously assessing the psychological status of the patient and the family. The theory of family systems also emphasizes the principle that a change in the status of one of the members can affect the balance of the entire family system, so cancer may change family roles, couple relationships, parent-child relationships, economic responsibilities, and decision-making style. In such a situation, the psycho-oncologist does not merely reduce the symptoms of anxiety or depression of a family member, but also tries to strengthen the communication function and adaptation of the entire system. In the diagnosis stage, psychological intervention can focus on processing the initial shock, managing uncertainty, correcting catastrophic perceptions, and creating an appropriate atmosphere for the expression of emotions. Many families are faced with a wealth of medical information at this stage and may not be able to properly receive, process, and remember information due to high anxiety, so the psycho-oncologist can increase the family's capacity to accompany the treatment process by teaching emotion regulation and effective communication skills. One of the important applications of this role is the initial assessment of family members' psychological distress, because family caregivers may encounter significant symptoms of anxiety, depression, sleep disturbance, fatigue, irritability, and caregiver burnout without considering themselves as sick. Early identification of these problems allows for preventive intervention and prevention of exacerbations of psychological disorders. The psycho-oncologist can also assess the level of distress, quality of life, caregiving burden, coping styles, and support needs of family members using clinical interviews and standard screening tools, and design an appropriate intervention based on the findings of the evaluation. In families where anxiety is prominent, breathing training, relaxation, attention regulation, cognitive restructuring, and coping skills can be effective in reducing emotional arousal, and in cases where there are catastrophic thought patterns, feelings of guilt, or excessive responsibility, cognitive-behavioral interventions can help correct these patterns. In situations where the family is facing a semantic crisis, feelings of injustice, or worry about death, existential and meaning-based approaches can allow for conversations about suffering, hope, family values, and the meaning of care. Another important area of intervention is therapeutic and family relationship education, as disagreements between family members about the amount of information that should be given to the patient, the way treatment decisions are made, or how to express concerns can create family tension. By facilitating family meetings, the psycho-oncologist can help members express their needs and concerns without blame and conflict, and move towards participatory decision-making. In families where the patient is a child or adolescent, this role becomes even more important, because in addition to tolerating their anxiety, parents must also manage the emotional and developmental needs of the child. Educating parents on how to talk to the child, answer questions about illness, manage fear of medical procedures, and maintain a sense of security can be part of psycho-oncological interventions. In advanced cancers or conditions where the prognosis is uncertain, psychological support should be directed towards tolerating uncertainty, preventing caregiver burnout, processing grief in advance, and maintaining meaningful communication between family members. In palliative care, a psycho-oncologist can help the family manage psychological suffering, communicate about care goals, make difficult decisions, and face the possibility of death. Family support at this stage does not mean eliminating grief or creating unrealistic hope, but rather aims to provide the conditions in which family members can maintain their communication capacity, emotional presence, and informed decision-making alongside the reality of the disease. On the other hand, after the end of active treatment, the family's needs do not necessarily end, and there may continue to be concern about the recurrence of the disease, changes in family roles, the patient's return to social and occupational activities, and adjustment to life after cancer. Therefore, the psycho-oncology should not limit family support to the treatment period, and consider periodic assessments and appropriate interventions during the survival phase. One of the important applications of this approach is to enhance the self-efficacy of family caregivers, as a caregiver who feels that he or she is not sufficiently capable of managing the patient's needs may experience anxiety, avoidance, or burnout. Training in problem-solving skills, care planning, setting healthy boundaries, sharing responsibilities, and using social resources can increase caregivers' sense of control and competence. A psycho-oncologist can also help the family balance patient care and self-care, as ignoring the caregiver's physical and psychological needs in the long term may reduce the quality of care and the health of the entire family system. From the perspective of group interventions, the formation of support groups for caregivers can provide the possibility of exchanging experiences, reducing loneliness, and increasing the perception of social support, and in addition, short-term family interventions can be used for families facing conflict or communication disorder. In recent years, the use of digital interventions and telepsycho-oncology has also made it possible to provide psychological support to families who are unable to visit regularly due to geographical distance, financial limitation, physical condition of the patient, or lack of specialists. However, the use of technology should be done with regard to information confidentiality, digital literacy, equal access, and quality of therapeutic communication. The main limitations in psychological support for families with cancer include the lack of trained specialists in the field of psycho-oncology, time constraints in therapeutic settings, the cost of services, the stigma associated with receiving psychological services, and the excessive focus of some health systems on physical indicators. Also, not all families have the same structure, culture, beliefs, and social resources, and for this reason, the use of a fixed protocol regardless of the family context can reduce the effectiveness of the intervention. Differences in the patient's age, type of cancer, stage of the disease, economic status, role of the primary caregiver, family structure, and severity of psychological symptoms should be considered in the design of the intervention program. Another limitation is the risk of ignoring family members who do not openly ask for help, so active and periodic evaluation should replace waiting for voluntary referrals. In cancer centers, it is suggested that family psychological support be defined as part of standard care rather than an ancillary service, and that screening for the psychological distress of the patient and caregivers be carried out at important points in the course of the disease. Establishing stage-based protocols from the time of diagnosis to active treatment, survival, relapse, and palliative care can increase the continuity of services. It is also essential for the psycho-oncologist to work closely with the oncologist, nurse, social worker, palliative medicine specialist, and other members of the multidisciplinary team to address the physical and psychological needs of the family in an integrated framework. Developing training programs for caregivers, creating support groups, purposeful use of telepsycho-oncology, designing family-centered cultural interventions, and teaching communication skills to treatment team members can improve the quality of psychological support. Finally, the role of the psycho-oncologist in the family of cancer patients can be considered beyond the treatment of a psychological symptom, this role includes assessment, prevention, education, facilitating communication, strengthening adaptation, supporting caregivers, intervening in the crisis, and accompanying the family at different stages of the cancer path, and its ultimate goal is to create conditions in which the patient and the family can maintain and strengthen the capacity to regulate emotion, communicate effectively, make informed decisions, maintain the quality of life, and rebuild the family balance as much as possible in the face of the disease, while accepting medical realities.