Background Caregiver depression and anxiety has been shown to negatively affect parenting and child development outcomes. However, little evidence has been gathered in Africa on this topic. This study assesses the relationship between caregiver mental health on parenting behaviors and developmental outcomes of children under five (CU5) in three African countries Methods A probability sample of 1232 primary caregivers of CU5 in Kenya, Tanzania and Malawi completed a structured questionnaire. Depression and anxiety were measured with the Hopkins Symptoms Checklist. Developmental milestones of CU5 were estimated via parental report. Bivariate associations between mental well-being and parent-child interactions and achievement of child developmental milestones were assessed with Chi-square tests. Results More caregivers in Kenya (61%) and Tanzania (60%) reported symptoms of depression than those in Malawi (21%, p<0.000). More caregivers in Kenya (64%) and Tanzania (61%) reported anxiety compared to those in Malawi (27%, p<0.000). No associations were found between depression and parent-child interactions. Caregivers without anxiety were more likely to read books (20% vs. 16%, p<0.05) or to count with the child (38% vs. 32%, p<0.05) than those with symptoms of anxiety. Depression had negative effects on children's fine motor and social-emotional development, whereas anxiety negatively affected fine motor, social-emotional and receptive language. Conclusion High levels of depression and anxiety were found among caregivers of CU5 in Kenya and Tanzania. Caregiver mental health negatively affected parenting behaviors and the attainment of age-appropriate developmental milestones in the three countries. Programs should address caregiver mental health to improve early child development.