Purpose: This study compared postpartum depression and parental self-efficacy between married immigrant women from Vietnam and native Korean mothers. Method: The participants were 72 native Korean mothers and 69 immigrant Vietnamese mothers living in a suburban city in South Korea. The instruments used were the Edinburgh Postnatal Depression Scale and the Parent Expectation Survey. Results: There were statistically significant differences in age, education, employment, income, husband's age, and family structure between the two groups. Immigrant Vietnamese mothers experienced higher levels of postpartum depression (t = -3.466, p = .001) and had lower parental self-efficacy (t = 5.607, p < .001) than native Korea mothers. Postpartum depression was negatively correlated with parental self-efficacy in native Korean mothers (r = -.349, p = .003), but there was no significant correlation in the immigrant Vietnamese mothers (r = .011, p = .936). The mothers' country of origin, whether immigrant or Korean, was a significant factor in postpartum depression (beta = .338, p = .040; R-2 = .091). The mothers' country of origin had no effect on parental self-efficacy (p = .957). Instead, significant differences were found for the age, education level, and family structure of the participant (R-2 = .036). Conclusions: The results of this study demonstrated that postpartum depression was more prevalent among married immigrant women from Vietnam than among native Korean mothers. Accordingly, a postpartum depression intervention program for married immigrant women should be developed and implemented.