PURPOSE: This study aimed to develop a post-traumatic growth (PTG) program, based on the PTG promotion resources suggested by Cahlhoun, Cann, and Tedeschi, and to apply it to breast cancer patients to determine its effect. METHODS: A non-equivalent control group pretest-posttest experimental design was used. In total, 74 participants were enrolled in this study, with 37 in the experimental group and 37 in the control group. The PTG program developed in this study consisted of writing and self-reflection for self-analysis, talking and sharing for self-disclosure, and participation in a self-help group for social support. The instruments used for this study were the Korean version of the Event Related Rumination Inventory, the Korean version of the Hospital Anxiety and Depression Scale, and the Korean version of the Post-traumatic Growth Inventory. The data were analyzed with the chi(2)test, t-test, Fisher's exact test and all analysis were conducted based on an intention-to-treat principle. RESULTS: The experimental group that underwent a PTG program had a lower emotional distress score than the control group (anxiety: t = -3.84, p = .001; depression: t = -3.22, p = .002). The experimental group had a lower intrusive rumination (t = -3.55, p = .001) and had higher deliberate rumination score than the control group (t = 2.10, p = .039). The experimental group had a higher PTG score than the control group (t = 2.34, p = .022). CONCLUSIONS: The PTG program developed in this study for breast cancer patients has the potential to contribute to the promotion of PTG in breast cancer patients.