Dihydroartemisinin (DHA)-piperaquine is being evaluated as intermittent preventive therapy for malaria, but dosing has not been optimized for children. We assessed exposure to DHA and piperaquine in Ugandan children at two ages during infancy. Intensive sampling was performed in 32 children at 32 weeks of age, 31 children at 104 weeks, and 30 female adult controls. Compared with adults, DHA area under the concentration-time curve (AUC_{0-8 hr} ) was 52% higher at 32 weeks and comparable at 104 weeks. Compared with adults, piperaquine AUC_{0-21 d} was 35% lower at 32 weeks and 53% lower at 104 weeks. Terminal piperaquine concentrations on days 7, 14, and 21 were lower in children compared with adults and lower at 104 compared with 32 weeks. Piperaquine exposure was lower in young children compared with adults, and lower at 104 compared with 32 weeks of age, suggesting a need for age-based DHA-piperaquine dose optimization for chemoprevention.