Background <p>Most women experience breastfeeding problems and reduced comfort due to postpartum problems and low breastfeeding self-efficacy. Mobile-based care applications are reported to provide supportive care in addressing these issues experienced by women during the postpartum period. This study was conducted to determine the effect of a mobile application- supported postpartum care program on breastfeeding self-efficacy and birth comfort.</p> Materials and methods <p>This randomized controlled trial was conducted between June 1, 2023 and December 30, 2023 with 80 women (experimental: <i>n</i> = 40, control: <i>n</i> = 40) who delivered by cesarean section and were staying in the postpartum wards of a hospital in the Mediterranean Region of Türkiye. CONSORT guidelines were followed in the study. Participants in the Experimental Group used a mobile postpartum care application installed on their phones during the postpartum period. They were asked to benefit from the educational content of the application. Live counseling was provided for women in this group in case of a problem. Participants in the Control Group were only given routine postpartum care.</p> Results <p>The women in the Experimental Group had higher mean scores 60.0 (3.75) on the post-test application of the Breastfeeding Self-Efficacy Scale than those in the Control Group 53.0 (5.75). In addition, it was determined that the women in the Experimental Group had higher mean scores (130.50 + 9.08) on the total and subscales of the Postpartum Comfort Scale and that the difference was statistically significant.</p> Conclusion <p>In conclusion, the mobile application-supported postpartum care program was an effective method to increase breastfeeding self-efficacy and postpartum comfort. Mobile health applications should be considered as a part of routine postpartum care to prevent and eliminate breastfeeding problems, raise the perception of breastfeeding self-efficacy, and increase comfort in the postpartum period.</p> Trial registration <p>This trial is registered with the Clinical Trial PRS with the identifier</p> <p>NCT05993936 (registration date 2023-09-22)</p>