Although online parenting programs have been growing fast recently, their effects on child maltreatment remains unknown. This meta-analysis aims to estimate the effectiveness of online parenting programs on child maltreatment-related outcomes and examine potential moderators associated with intervention effects. Seven electronic databases were systematically searched for quasi-experimental and randomized controlled trials published before January 15, 2024. Sixteen studies were included, which yielded 24 effect sizes. The overall effect indicated significant reductions in caregiver reports of child maltreatment (standardized mean difference [SMD] = −0.17, 95% CI [−0.30, −0.04]), with the most substantial effects on improving inappropriate parenting attitudes and cognition (SMD = −0.63 [−1.11, −0.16]). Subgroup analyses revealed that intervention location and sample source significantly moderated the effectiveness of online parenting programs, with studies conducted outside the United States and recruiting participants from primary care clinic settings showing larger effect sizes. Additionally, interventions without human interactions or action tasks, targeting individuals, delivered asynchronously, and with shorter durations showed larger effects. These findings suggest that online parenting program is a promising strategy in preventing child maltreatment, and future research can develop more effective online parenting programs to protect children.