Objective: This study examines the effectiveness of a quasi-experimental, pre-post intervention delivered by medical social workers using the “Four-Whole” care model for breast cancer patients. Methods: The intervention addresses holistic rehabilitation by integrating physical, psychological, social, and spiritual dimensions, aiming to enhance patients’ breast cancer knowledge, sense of meaning in life, perceived social support, and affect regulation. Sixty-one female participants were randomly assigned to either an intervention group (n = 31), which received 12 weeks of “Four-Whole” care, or a control group (n = 30), which received standard care. Results: Repeated-measures ANOVA revealed significant group-by-time interaction effects across all outcome variables (F(1,59) ≥ 8.38, p < 0.01). Compared to the control group, the intervention group showed significantly greater improvements in breast cancer knowledge (η2 = 0.50), meaning in life (η2 = 0.12), social support (η2 = 0.15), positive affect (η2 = 0.21), and regulation of negative affect (η2 = 0.17). Conclusion: These findings suggest that the “Four-Whole” care model, when delivered by medical social workers, can significantly improve multidimensional rehabilitation outcomes for women with breast cancer.