PURPOSE: The aims of the study were to develop mobile application for postpartum care of first-time mothers and to validate it's effect. METHODS: Using a nonequivalent control group pretest-posttest design, 52 first-time mothers were recruited (26 each in experimental and control) and the experimental group used the mobile application for 6 weeks after delivery. Postpartum self-care knowledge and confidence, infant care knowledge and confidence, and postpartum depressive mood (Edinburgh Postnatal Depression Scale) were measured before discharge from the hospital and 6 weeks later. RESULTS: Women who have used the postpartum care mobile application reported higher levels of postpartum self-care knowledge (p=.030) and confidence (p=.023) infant care knowledge (p=.001) and confidence (p=.004), while scores of postpartum depression (p=.021) were lower than those in the control group. CONCLUSION: The postpartum-care mobile application developed in this research may be effective in reinforcing knowledge and confidence for postpartum self-care and infant care and in reducing postpartum depressive mood.