Background: Breast cancer is one of the most commonly diagnosed cancers among women. Health services for breast cancer patients should give high priority to the social and psychological realities experienced by those dealing with the ramifications of their illness. Psychosocial interventions and group counseling for patients have been shown to be highly effective in the care of breast cancer patients. Objective: This study was conducted to determine the effects of group counseling on the adaptation of breast cancer patients to their illness. Methods: Sessions are made weekly, and each session lasted about 1.5 to 2 hours, and the researchers attended all sessions together. Pretests were administered to the patients at the first of the 10 group sessions, and posttests were administered at the last group session. Pretest/posttest pattern data were collected from 56 breast cancer patients using the Ways of Coping Inventory, the Psychosocial Adjustment to Illness Scale-Self-report, and the Multidimensional Scale of Perceived Social Support. These were evaluated using the SPSS 9.0 statistical package. Results: After group counseling, patients showed an increase in their positive perceptions of social support, psychosocial adaptation, and in their abilities to cope with breast cancer. Conclusions: The findings indicate that this group-counseling program positively affected patients' perceived social support and enhanced their abilities to effectively cope with stress. Implications for Practice: Cancer patients can have various problems in the adaptation process to cancer. Therefore, oncology nurses should be actively involved in working with patients to find solutions and ways of coping with the issues they face.