BACKGROUND : Besides physical and mental changes from childbirth, first-time mothers are also confronted with challenges associated with the demands of adapting to their roles as new parents. While positive effects of home-based psychoeducation intervention for mothers have been demonstrated, limited studies have developed and examined more accessible and cost-effective web-based psychoeducational interventions for mothers. OBJECTIVE : To examine the effectiveness of web-based and home-based postnatal psychoeducational interventions for first-time mothers during the early postpartum period. METHODS : A randomized controlled three-group pre-test and post-tests experimental design was adopted. Data were collected over five months, from October 2016 to August 2017, in a public tertiary hospital in Singapore from 204 primiparas who were randomly allocated to the web-based psychoeducation group, the home-based psychoeducation group, or the control group. The measured outcomes included maternal parental self-efficacy, social support, psychological well-being, satisfaction with postnatal care, and cost-effectiveness evaluation. Data were collected at four time points: the baseline, and three post-tests at one month, three and six months post-delivery. RESULTS : When compared to the control group, the web-based intervention improved self-efficacy at post-test 1 (mean difference = 2.68, p = 0.028) and reduced postnatal depression at post-test 3 (mean difference = -1.82, p = 0.044), while the home-based intervention did not show significant effect on these two outcomes at all post-tests. Both web-based and home-based interventions helped mothers to get better social support at all post-tests than those in the control group. Mothers in both web-based and home-based intervention groups were more satisfied with the postnatal care than those in the control group at all post-test time points (except for web-based group at post-test 1). There were no differences in anxiety scores among the three groups. When compared to the home-based intervention, the web-based intervention showed noninferior effect on all outcomes at all post-tests. CONCLUSIONS : The web-based intervention had better effects on improving self-efficacy, social support, and postnatal depression, which should be introduced to first-time mothers for better postnatal care.