Objective: Studies available on cognitive function among school-aged HIV-infected African and in particular Nigerian children are few. The purpose of the study was to assess the neurocognitive function of a group of HIV-infected schoolaged (6 - 15 years) children using the Raven’s Standard Progressive Matrices (RPM). Method: Cognitive assessments of 69 HIV positive children and 69 age- and sex-matched apparently healthy HIV negative control children were performed using the Raven’s Standard Progressive Matrices (RPM). The children were subdivided (Piaget’s developmental staging) into two sub-groups: the concrete operation stage (6 - 11 years) and the formal operation stage (12 - 15 years) for analysis. Result: The mean RPM score for the HIV positive children was 18.2 (8.0 - 47.0, SD 9.8) which was significantly lower than the score of 27.2 (8.0 - 52.0, SD 13.8) for the HIV negative children (p < 0.001). On the RPM grading and using the HIV negative children as the standard, 56.5% of the HIV positive children had cognitive performance at below average to intellectually defective range. Conclusion: School-aged HIV positive children had significantly lower cognitive scores compared with age and gender-matched HIV negative children. Routine neuropsychological evaluation of all school-aged HIV-infected children is recommended. Early detection of cognitive impairment will help in planning appropriate interventions.