The effect of family-based psycho-oncological interventions on patient adherence to treatment and family participation in care is one of the important axes in comprehensive cancer care, because the cancer treatment process usually requires continuous cooperation of the patient, family, and treatment team, and the quality of this cooperation can affect the treatment experience and continuity of care. Adherence to treatment in cancer is a multidimensional concept and can include regular attendance at treatment sessions, correct use of prescribed medications, observance of medical recommendations, periodic tests and follow-ups, and proper communication with the treatment team. On the other hand, family involvement is not limited to caring affairs and includes dimensions such as emotional support, practical assistance, accompaniment in referrals, facilitating communication with the treatment team, supporting informed decision-making, and paying attention to the patient's psychological needs. The theoretical foundations of family-centered interventions are based on the bio-psychosocial model, the theory of family systems, the theory of self-efficacy, and the participatory care approach, and emphasizes the principle that treatment-related behaviors are not formed in a vacuum, but are influenced by the family environment, the patient's beliefs, the quality of relationships, social resources, and the emotional experience of the disease. A cancer diagnosis can reduce a patient's sense of control, and anxiety, fear of complications, depression, or hopelessness may affect his ability to follow a treatment plan regularly. In such a setting, targeted family support can serve as an important source of reinforcement of caring behaviours, provided that support is provided in an appropriate and non-controlling manner. In family-centred interventions, the psycho-oncologist first assesses the patient-family interaction pattern, the amount of support available, possible conflicts, beliefs about cancer and treatment, and psychological barriers to adherence. This assessment helps to identify factors that may hinder the patient's active participation, for example, intense fear of complications, misconceptions about the effectiveness of treatment, feelings of uselessness, communication problems, or excessive pressure from family members. One of the important goals of the intervention is to increase the patient's self-efficacy, i.e. the patient feels capable of participating in the management of the disease and implementing treatment recommendations. The psycho-oncologist can help the patient take a more active role in self-care through education, setting achievable goals, and strengthening problem-solving skills. At the same time, the family is also trained to strengthen the patient's independence and abilities rather than doing everything for the patient. Family support can be constructive when it leads to an increased sense of empowerment, rather than making the patient dependent or passive. In the cognitive-behavioral approach, dysfunctional beliefs about treatment and illness are examined. Some patients may perceive complications as ineffective or avoid continuing treatment due to an unpleasant experience of a course of treatment. Some families may also develop negative attitudes toward treatment based on unscientific information or the experience of those around them. A psycho-oncologist can help identify these beliefs and correct unrealistic perceptions, while specialized information about the benefits, risks, and complications of treatment should be provided by the medical team. Family psychological education about the importance of regular follow-up, stress management, and patient support practices can lead to greater coordination in the home environment. Another important application of family-centered interventions is communication skills training. An open conversation about the patient's fears, complications, needs, and family concerns can prevent misunderstandings and conflicts. A psycho-oncologist can teach family members how to encourage the patient to pursue treatment recommendations without threats, blame, or pressure. There is an important difference between "support" and "control"; support involves accompaniment, listening, and helping tailored to the patient's needs, while extreme control may reduce the patient's sense of independence and create resistance. Family involvement in care planning can also help organize daily affairs. Adjusting the timing of medications as directed by the doctor, scheduling commutes, accompanying medical visits, recording questions, and paying attention to the recommendations of the treatment team are some of the activities that can be done with the participation of the family if the patient is satisfied. The use of reminder and planning tools can also be helpful for patients who experience forgetfulness due to stress or a high volume of information. However, such tools should complement medical advice and should not replace communication with the treatment team. Family-centered interventions can also help manage negative emotions, as the anxiety and depression of the patient or family may make the process of participating in treatment difficult. Emotion regulation training, relaxation and problem-solving skills can help the family react more adaptively in stressful situations. In some cases, joint family meetings can be used to address conflicts that directly affect care. If the patient and the family disagree about the amount of treatment, the type of care, or the method of support, the psycho-oncology can lead the conversation toward articulating the needs and values of each party, without being in the position of the medical decision-maker themselves. Respect for the patient's autonomy and the right to participate in treatment decisions are fundamental principles of this process. In the case of pediatric patients or individuals who depend on others for certain caregivings, the role of the family may be broader and needs to be adjusted according to the patient's age, decision-making capacity, and circumstances. Another important application of these interventions is to reduce the burden of family care through the division of responsibilities, as caregiver burnout may ultimately reduce the quality of patient support. A psycho-oncologist can help the family identify available sources of support and divide responsibilities among eligible members. Family involvement can also be formed through strengthening communication with the treatment team. Training the family to prepare a list of questions, record important information, and accurately express the patient's concerns can increase the quality of interaction with the treatment team. The psycho-oncologist plays the role of the psychological coordinator, but the responsibility for providing medical information and making decisions about the treatment regimen rests with the relevant professionals. The important challenge in implementing family-centered interventions is the difference between optimal support and extreme intervention; a family that controls the patient too much may unintentionally increase their anxiety and resistance. Another challenge is conflict between family members, differences in therapeutic beliefs, economic pressure, time constraints, and difficulty in accessing psychological services. Some families may also not consider it necessary to see a mental health professional due to cultural beliefs or traditional attitudes about the disease. On the other hand, some patients are reluctant to share all their medical or psychological information with family members, which highlights the need to observe confidentiality and patient satisfaction. Another limitation is that adherence to treatment is influenced by several factors and its change cannot be attributed solely to psychological intervention, such as the type of cancer, the complexity of treatment, complications, economic status, access to services, and the quality of communication with the health system. Therefore, psycho-oncological interventions should be used in conjunction with medical, nursing, social and other services. It is suggested that family evaluation be done from the beginning of the treatment process and psychological support should be continued in accordance with the changing needs of the patient and the family. Designing educational programs for patients and caregivers, joint family meetings, effective communication training, strengthening patient self-efficacy, and periodic monitoring of psychological distress can provide a suitable framework for family-centered interventions. Also, the use of distance counseling can increase access to support in families who are unable to visit regularly due to geographical distance or caring responsibilities. Ultimately, the goal of family-centered psycho-oncological interventions is not to force the patient to follow the treatment or transfer the responsibility of treatment to the family, but to create a supportive environment in which the patient can participate in self-care with more awareness and self-efficacy, and the family can play its role in an effective, respectful, and appropriate manner to the patient's needs. Such an approach can strengthen the patient-family relationship, reduce psychological barriers to participation in treatment, and pave the way for the formation of a participatory and sustainable care model along the path of cancer treatment.