One of the biggest threats to early childhood development in Africa is poor maternal mental health. The present study reports on the relationships between clinical diagnoses of persistent maternal mental health disorders (at 3- and/or 6- and 18-month post-term age) and toddler neurodevelopment at 18 months of age. Eighty-three mother–toddler dyads from low socio-economic status settings in Cape Town, South Africa, were included. At the 3-, 6- and 18-month postnatal visits, clinician-administered structured diagnostic assessments were carried out according to the Diagnostic and Statistical Manual of Mental Disorders-V (DSM-V) criteria. Toddler neurodevelopment at 18 months corrected age was assessed with the Bayley Scales of Infant and Toddler Development (BSID-III). No significant differences (p> 0.05) were found between toddlers with exposure to persistent mood or psychotic disorders in the different BSID-III domains compared to toddlers with no exposure. Toddlers exposed to persistent comorbid anxiety and mood disorders scored significantly higher on the cognitive (p= 0.049), motor (p= 0.013) and language (p= 0.041) domains and attained significantly higher fine motor (p= 0.043) and gross motor (p= 0.041) scaled scores compared to toddlers with no maternal mental health disorder exposure. Future investigations should focus on the role of protective factors to explain the pathways through which maternal mental health status is associated with positive toddler neurodevelopmental outcomes.