Purpose: Purpose of this study was to examine the effects of the Mindfulness Meditation program on perceived stress, ways of coping, salivary cortisol level, and psychological stress response in patients with breast cancer. Methods: This was a quasiexperimental study with a non-equivalent control group pre-post test design. Participants in this study were 50 patients who had completed breast cancer treatment (experimental group, 25, control group, 25). The experimental group received the Mindfulness Meditation program for 3 hours/session/ week for 8 weeks. Data were analyzed using $X^2$-test and t-test for subject homogeneity verification, and ANCOVA to examine the hypotheses. Results: The experimental group had significantly lower scores for perceived stress, emotional focused coping, salivary cortisol level, and psychological stress response compared to the control group. However, no significant differences were found between two groups for the scores on problem focused stress coping. Conclusion: According to the results, the Mindfulness Meditation program was useful for decreasing perceived stress, emotional focused coping, salivary cortisol level, and psychological stress response. Therefore, this program is an effective nursing intervention to decrease stress in patients with breast cancer.