Background: This study aimed to enhance post-traumatic growth in young breast cancer patients by providing them with self-disclosure and social support resources, to reduce intrusive rumination and increase deliberate rumination. This study was conducted at a university-based cancer center in Seoul, South Korea. The study included a four-week group-based psychoeducational program, which supported the post-traumatic personal growth of breast cancer patients. The primary outcome was increased post-traumatic growth, and the secondary outcomes were rumination, distress, and traumatic perception. Methods: The study included 38 young breast cancer patients, with a mean age of 42.21 years and mean time since diagnosis of 13.84 months. Results: Results of the study revealed statistically significant improvements in total post-traumatic growth and all subdomains, after the intervention (p < 0.001) and one month later (p < 0.001), as compared to the baseline. A significant improvement was also observed in deliberate rumination after the intervention (p = 0.038). Furthermore, the patients had a statistically significant decrease in anxiety, after the intervention (p = 0.035) and one month later (p = 0.005), as compared to the baseline. Conclusions: Overall, the program encourages activities that promote post-traumatic growth, enabling young breast cancer patients to return to their normal lives. Specifically, the growth allows patients to return to work and maintain a healthy body and mind. The results of this study indicate that this program can be used as an effective psychological intervention for young breast cancer patients.