Purpose: This study aimed to verify the effects of prenatal breast self-massage education on first-time mothers' breastfeeding self-efficacy, breastfeeding adaptation, and breastfeeding practice. Method: The experimental group (n=26) received prenatal breast self-massage education focused on self mamma care (SMC) at 34-36 weeks gestation and 2 weeks later face-to-face. The control group (n=25) was recruited immediately following birth and received usual care. Breastfeeding self-efficacy was measured 4 hours after childbirth and 3 days later, and breastfeeding practice, breastfeeding adaptation, and breastfeeding-related characteristics were measured 2 weeks and 4 weeks after childbirth through online survey. The data were analyzed by x2 test and t-test using SPSS/WIN 24.0. Results: There was no significant difference in breastfeeding self-efficacy of the experimental group at 4 hours after childbirth (t=0.83, p=.410) whereas it was statistically significantly higher at 3 days postpartum (t=2.86, p=.006). There were no significant differences in breastfeeding adaptation between the two groups at both 2 weeks (t=1.76, p=.084) and 4 weeks postpartum (t=0.87, p=.388). For breastfeeding practice a statistically significant difference was found at 4 weeks for the experimental group ($x^2=4.77$, p=.036). Conclusion: This antenatal SMC intervention was found to be a feasible intervention for use in clinical practice.