Aim: to assess the efficacy of psychosocial interventions delivered through task-sharing approaches for preventing perinatal common mental disorders among women in low- and middle-income countries. Methods: We conducted a systematic review of randomized controlled trials following a prespecified protocol registered in the Open Science Framework (osf.io/qt4y3). We searched MEDLINE, Web of Science, PsycINFO, and Cochrane Central Register of Controlled Trials (CENTRAL) through June 2022. Two reviewers independently extracted the data and evaluated the risk of bias of included studies using the Cochrane risk of bias tool. We performed random-effects meta-analyses and rated the certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results: We included 23 studies with 24,442 participants. At post-intervention, task-shared psychosocial interventions, were effective in preventing the development of mental disorders in general (RR 0.57, 95% CI [0.35, 0.91]), and specifically depression (RR 0.51, 95% CI [0.35, 0.75]), but not anxiety disorders (RR 0.46, 95% CI [0.06, 3.33]). Similarly, psychosocial interventions reduced psychological distress (SMD −1.32, 95% CI [−2.28, −0.35]), and depressive symptoms (SMD −0.50, 95% CI [−0.80, −0.16]), and increased parenting self-efficacy (SMD −0.76, 95% CI [−1.13, −0.38]) and social support (SMD −0.72, 95% CI [−1.22, −0.22]). No effect was detected for anxiety symptoms at post-intervention. At follow-up the beneficial effects of interventions progressively decreased. Conclusions: Psychosocial interventions delivered through the task-sharing modality are effective in preventing perinatal common mental disorders and fostering positive mental health among women in low- and middle-income countries. However, our findings are tentative, due to the low number of preventative intervention strategies considering outcomes as the incidence of mental disorders, especially in the long-term. This evidence supports calls to implement and scale up psychosocial prevention interventions for perinatal common mental disorders in low- and middle-income countries.