This paper aimed to assess the impact of maternal common mental disorders (CMD) among caregivers living with HIV on the cognitive functioning of their child. Data were collected at baseline and 12 months follow-up from mother–child dyads recruited as part of an ongoing trial in Zimbabwe. Symptoms of CMD were assessed using the Shona Symptom Questionnaire. Mixed-effects linear regression was used to assess child cognitive scores at follow-up (using the Mullen Scales of Early Learning) in relation to caregiver CMD prevalence over 12 months. At baseline, caregivers reporting CMD (n = 230; 40.1%) were less likely to have completed higher education (46.9% vs. 56.9%; p = 0.02), more likely to be unmarried (27.8% vs. 16.0%; p