BACKGROUND: Programs for the prevention of mother-to-child transmission (PMTCT) of human immunodeficiency virus (HIV) have been scaled up in many low- and middle-income countries. However, HIV drug resistance (HIVDR) data among HIV-1-infected young children remain limited. METHODS: Surveys of pretreatment HIVDR among children aged <18 months who were diagnosed with HIV through early infant diagnosis were conducted in 5 sub-Saharan African countries (Mozambique, Swaziland, South Africa, Uganda, and Zimbabwe) between 2011 and 2014 following World Health Organization (WHO) guidance. Deidentified demographic and clinical data were used to explore risk factors associated with nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance. RESULTS: Among the 1450 genotypes analyzed, 1048 had accompanying demographic and clinical data. The median age of children was 4 months; 50.4% were female. HIV from 54.1% showed resistance to 1 or more antiretroviral (ARV) drugs, with 53.0% and 8.8% having resistance to 1 or more NNRTI or nucleoside reverse transcriptase inhibitors, respectively. NNRTI resistance was particularly high in children exposed to ARV drugs through PMTCT; adjusted odds ratios were 1.8 (95% confidence interval [CI], 1.3-2.6) for maternal exposure only and 2.4 (CI, 1.6-3.6) for neonatal exposure only. CONCLUSIONS: Protease inhibitor-based regimens in children aged <3 years are currently recommended by WHO, but the implementation of this recommendation is suboptimal. These results reinforce the urgent need to overcome barriers to scaling up pediatric protease inhibitor-based regimens in sub-Saharan Africa and underscore the need to accelerate the study and approval of integrase inhibitors for use in young children.