Aims. Observational studies have shown a relationship between maternal mental health (MMH) and child development, but few studies have evaluated whether MMH interventions improve child-related outcomes, particularly in low- and middle-income countries. The objective of this review is to synthesise findings on the effectiveness of MMH interventions to improve child-related outcomes in low- and middle-income countries (LMICs). Methods. We searched for randomised controlled trials conducted in LMICs evaluating interventions with a MMH component and reporting children's outcomes. Meta-analysis was performed on outcomes included in at least two trials. Results. We identified 21 trials with 28 284 mother-child dyads. Most trials were conducted in middle-income countries, evaluating home visiting interventions delivered by general health workers, starting in the third trimester of pregnancy. Only ten trials described acceptable methods for blinding outcome assessors. Four trials showed high risk of bias in at least two of the seven domains assessed in this review. Narrative synthesis showed promising but inconclusive findings for child-related outcomes. Meta-analysis identified a sizeable impact of interventions on exclusive breastfeeding (risk ratio = 1.39, 95% confidence interval (CI): 1.13-1.71, ten trials, N = 4749 mother-child dyads, I² = 61%) and a small effect on child height-forage at 6-months (std. mean difference = 0.13, 95% CI: 0.02-0.24, three trials, N = 1388, I² = 0%). Meta-analyses did not identify intervention benefits for child cognitive and other growth outcomes; however, few trials measured these outcomes. Conclusions. These findings support the importance of MMH to improve child-related outcomes in LMICs, particularly exclusive breastfeeding. Given, the small number of trials and methodological limitations, more rigorous trials should be conducted.