ObjectiveThe study aims to investigate positive and negative social interactions as predictors of maternal self-efficacy and to examine the mediating role of postpartum fatigue. DesignParticipants included 450 Arab and Jewish mothers of healthy one-month-old infants who visited 14 well-baby care clinics located in northern Israel. The study used a prospective longitudinal cohort design. Participants completed the first questionnaire and agreed to a follow-up phone interview three months later. Both ethnic groups had a response rate of 90% for the follow-up interview. The questionnaire included six scales that measured socioeconomic status and demographics, obstetric characteristics, social networks and support, negative social interactions, fatigue and maternal self-efficacy (MSE). The phone interview was a shorter version of the written questionnaire focusing on MSE and fatigue. Maternal self-efficacy four month after birth was examined with social support, negative interactions and fatigue, using multiple linear regressions within each ethnic group. FindingsIn both groups, negative social interactions decreased perceptions of maternal self-efficacy. Women who reported higher social support after birth experienced a greater sense of maternal self-efficacy four months after birth, though the association was stronger among Jewish women. Post-partum fatigue affects Arab and Jewish mothers differently. Among Arab mothers, fatigue at one month mediates MSE as well as the relationship between social support and negative interactions at four months. Among Jewish mothers, these factors are directly related to MSE, with no mediation effect. Implications for practiceThe correlations found between social interactions, fatigue and maternal self-efficacy can be useful in providing appropriate care that includes information and parental support. Health professionals working with postpartum women must assess degree of postpartum fatigue and negative postpartum social interactions as well as social support during the postpartum period.