Purpose: This study was to test a theoretical model examining the relationships among social support, illness demands, marital adjustment, family coping and family functioning in couples more than three years after breast cancer diagnosis. Methods: A causal modeling methodology was used to test the specified relationships in the recursive theoretical model. A total of 60 couples with breast cancer were recruited from January to April 2005. Five standardized questionnaires were used to measure the theoretical concepts: social support (ISSB), illness demands (DOII), marital adjustment (DAS), family coping (F-COPES), and family functioning (FACESII). Results: Path analysis results from the wives and the husbands revealed different patterns. Three hypotheses were supported in the wife model as predicted: social support and family coping, family coping and family functioning, and social support and marital adjustment (trend). Five hypotheses were supported in the husband model as predicted: social support and illness demands, also social support and marital adjustment, illness demands and marital adjustment, marital adjustment and family coping, and family coping and family functioning. Conclusion: This study provides valuable information for developing various interventions with social support for improving family functioning of breast cancer couples in the middle adaption stage (more than three years after diagnosis).