Objective: This case report aims to illustrate the clinical trajectory of a woman diagnosed with early-stage breast cancer who developed prolonged grief following the loss of her sister to the same illness, and to explore the therapeutic effectiveness of a dual-focused intervention. Case: The patient presented with depressive symptoms, anxiety, avoidance behaviors, and diminished self-worth while navigating both cancer-related distress and bereavement. She received a sequential therapy plan consisting of individual cognitive-behavioral therapy (12 sessions) followed by a structured, group-based CBTgrief protocol (12 sessions). During the intervention, clinically significant reductions were observed in symptoms of depression and grief-related avoidance. In parallel, improvements were noted in self-compassion, meaning-making, and interpersonal functioning. Conclusion: This case underscores the therapeutic relevance of combining individual and group-based interventions in patients coping with concurrent cancer diagnosis and traumatic grief. It also highlights the role of sociocultural dynamics—including gender norms, identity disruption, and body image—in shaping the psychological experience and recovery process in Turkish female cancer patients. The report contributes to the psycho-oncology literature by demonstrating how dual-process grief interventions can be effectively tailored within a culturally sensitive framework.