Family-centered psycho-oncology is one of the important approaches in the comprehensive care of cancer patients, which does not consider the disease as merely an individual experience, but rather as an event that affects the entire family system. In this approach, the family is considered as part of the patient's psychological treatment, adjustment, and rehabilitation, and the interaction between the patient, family members, and the treatment team becomes of fundamental importance. A cancer diagnosis can cause a sudden change in family roles, responsibilities, emotional relationships, economic status, and communication patterns, and upset the previous balance of the family. From a theoretical perspective, social support is one of the protective factors against the psychological consequences of chronic and life-threatening diseases. Family support can appear in the form of emotional, informational, instrumental, financial, and accompaniment in the treatment process. Emotional support includes empathy, acceptance, active listening, and creating a sense of security for the patient, and can play a role in reducing feelings of loneliness and helplessness. Informational support also helps the patient to better understand information about the disease, treatment, complications, and coping strategies. Instrumental support includes accompaniment to medical visits, managing daily affairs, caring for the child or the elderly, and assisting with activities that the patient is unable to perform during treatment. Within the framework of stress and coping theory, cancer as a serious stressor can overwhelm a person's coping resources. In such a situation, the family can increase the patient's coping capacity as one of the most important external coping resources. Proper family support may help the patient assess the illness more manageable and feel more self-efficacious in the face of treatment. On the other hand, dysfunctional family communication can exacerbate the patient's anxiety, conflict, guilt, or social isolation. Therefore, the mere presence of the family does not imply effective support, and the quality of the relationship, the type of interaction, and the degree of appropriateness of support to the patient's actual needs are more important.