This study examined whether maternal depression is related to Early Childhood Developmental (ECD) delay among children by quantifying the mediating contribution of responsive caregiving. We used data from 1235 children (Children's mean age = 50.4 months; 582 girls, 653 boys, 93.9% were Han), selected through convenience sampling, in 2021. 4.7% of children had ECD delay, 34.3% of mothers had depression. Children with depressed mothers were less likely to receive responsive caregiving (OR 4.35, 95% CI 2.60-7.27), and those who did not receive responsive caregiving were more likely to experience ECD delay (OR 3.89, 95% CI 1.89-8.02). Responsive caregiving partly mediated the relationship between maternal depression and ECD. Early intervention for children with depressed mothers is worthy of further investigation.