The diagnosis of malignancy can act as a critical event for the patient and the family, affecting the psychological, relational, and social balance of the family in a short time, as family members are suddenly faced with a reality that may be accompanied by fear of death, worry about the future, ambiguity about treatment, changing family roles, and economic pressures. A family psychological crisis after a diagnosis of malignancy does not necessarily mean the presence of a mental disorder, but can be considered as an intense and temporary reaction to a threatening event that, if properly identified and supported, has the capacity to become a healthy adjustment. In this stage, the psycho-oncologist plays a key role in assessing the severity of the crisis, stabilizing emotion, reducing distress, facilitating communication, and activating family support resources. From the perspective of theoretical foundations, the biological, psychosocial, spiritual approach emphasizes that the crisis caused by cancer should be investigated in relation to the patient's physical condition, the psychological conditions of family members, interpersonal relationships, socioeconomic status, and belief systems. Also, the theory of family systems shows that the diagnosis of a serious illness in one member can disturb the balance of the entire family system, and the reaction of each member affects the reaction of the other members. Therefore, the psycho-oncologist does not examine the crisis solely as an individual problem of the patient or a specific caregiver, but rather considers the pattern of reaction of the whole family. The first step is to conduct a psychological assessment and identify the level of distress, anxiety, depression, agitation, sleep disturbances, catastrophic thoughts, feelings of helplessness, and family support resources. One of the important principles of crisis management is to create psychological stability and reduce emotional arousal, so the use of relaxation skills, controlled breathing, focusing on the present, and directing attention can be used in situations of severe anxiety. At this stage, providing information beyond the family's processing capacity may increase distress, so a psycho-oncologist can help the family receive and prioritize medical information step by step. Coordination with the medical team is also essential so that the messages presented to the family are coherent and based on valid information. Managing catastrophic thoughts is another important component of the intervention, as the family may consider the worst-case scenario to be certain immediately after hearing the word malignancy. Cognitive interventions can help members distinguish between their diagnosis, available information about the stage and prognosis, and their subjective perceptions, and avoid drawing definitive conclusions without sufficient evidence. The psycho-oncologist can also teach the skill of tolerating uncertainty, as many treatment decisions are made after medical reviews have been completed, and efforts to achieve complete certainty immediately may increase anxiety. One of the important uses of crisis intervention is to maintain healthy communication between family members, as the stress of the diagnosis may lead to silence, blame, anger, or disagreements about how to make decisions. Family meetings with a psycho-oncologist can provide a good space to express concerns, clarify roles, and reduce misunderstandings. In cases where family members disagree about the amount of information that should be given to the patient, the psycho-oncologist can help form a dialogue based on respect for the patient's preferences and the principles of therapeutic communication. In families where the patient is a child or adolescent, crisis management requires simultaneous attention to the parent's reaction and the child's developmental needs. Parents may hide information about the illness from the child due to fear of psychological harm, while the child may perceive the change in parental behavior and the therapeutic environment, and the lack of an appropriate explanation can increase anxiety. The psycho-oncologist can prepare the parent to communicate honestly, simply, and supportively, depending on the child's age and level of understanding. In the family of the adult patient, the role of the spouse, children, and other caregivers in crisis management should also be considered, and all responsibilities should not be focused on one person. Activating social support is another pillar of intervention, as a family that feels alone in the face of illness may experience more distress. Identifying family members, friends, social resources, support groups, and social services can reduce some of the practical and emotional stress of the crisis. In the event of economic problems, the psycho-oncologist can coordinate with the social worker to refer the family to appropriate resources, as financial stress can directly affect anxiety and family conflict. In some families, the diagnosis crisis is accompanied by a crisis of meaning, and questions about justice, death, hope, the future, and the meaning of life are raised. In these situations, the use of existential and meaning-based approaches can help family members process the experience of illness within the framework of their own values and beliefs, without denying the medical reality of the disease. The psycho-oncologist should also strengthen the family's capacity for decision-making, as intense anxiety can reduce the ability to process information and compare treatment options. Breaking complex decisions into smaller steps, recording questions, and encouraging the family to actively participate in therapeutic conversations can increase the sense of control. If psychological symptoms are severe, persistent, or accompanied by immediate danger, referral to a psychiatrist or other mental health professional is essential, and crisis management should be carried out within the framework of a multidisciplinary team. Once the initial crisis has stabilized, the intervention should be directed towards preventing long-term outcomes and preparing the family for the course of treatment, changing roles, possible complications, patient care, and adaptation to new circumstances. Important limitations of family mental crisis management include high intensity of excitement in the first days, lack of specialist time in therapeutic settings, limited access to psycho-oncology services, cultural differences, and difficulty in assessing the needs of members who do not openly seek help. Also, the family's response to the diagnosis of malignancy is influenced by the type of cancer, stage of the disease, the age of the patient, psychological history, economic resources, family structure, and the quality of pre-illness relationships, and it is not possible to apply a fixed intervention model for all families. Another limitation is the possibility of focusing too much on immediate sedation and ignoring long-term psychosocial needs, while effective crisis management should move from initial stabilization to sustainable adaptation. It is suggested that psycho-oncology services be integrated into the cancer care pathway from the time the diagnosis is announced, and that families with high distress be identified and supported at an early stage. Developing specific protocols for crisis assessment, emotional stabilization, communication with family, psychological education, and specialist referral can increase the quality of services. Also, teaching family communication skills to doctors and nurses can prevent the creation of ineffective communication at the time of diagnosis announcement. It is also important to use short-term follow-ups after the diagnosis is announced, as some psychological reactions become apparent in the following days and may not be visible in the initial assessment. Overall, the role of the psycho-oncologist in managing the psychological crisis in the family after a diagnosis of malignancy includes assessment, emotional stabilization, distress reduction, education, communication facilitation, decision-making enhancement, activation of social support, and prevention of burnout and persistent psychological disorders. The goal of these interventions is not to eliminate the most natural human reactions such as fear, sadness, or worry, but rather to help the family move through the crisis phase in an orderly manner and turn a sudden and threatening experience into a more manageable process so that family members can maintain their mental health, communication, and social functioning as much as possible while supporting the patient.