Background: The effect of hepatitis C virus (HCV) coinfection on CD4+T cell recovery in treated HIV-infected children is poorly understood. Objective: To compare CD4+ T cell recovery in HIV/HCV coinfected children with recovery in HIV monoinfected children. Method: We studied 355 HIV monoinfected and 46 HIV/HCV coinfected children receiving antiretroviral therapy (ART) during a median follow-up period of 4.2 years (interquartile range: 2.7-5.3 years). Our dataset came from the Ukraine pediatric HIV Cohort and the HIV/HCV coinfection study within the European Pregnancy and Paediatric HIV Cohort Collaboration. We fitted an asymptotic nonlinear mixed-effects model of CD4+ T cell reconstitution to age-standardized CD4 counts in all 401 children and investigated factors predicting the speed and extent of recovery. Results: We found no significant impact of HCV coinfection on either preART or long-term age-adjusted CD4 counts (z scores). However, the rate of increase in CD4 z score was slower in HIV/HCV coinfected children when compared with their monoinfected counterparts (P < 0.001). Both monoinfected and coinfected children starting ART at younger ages had higher preART (P < 0.001) and long-term (P < 0.001) CD4 z scores than those who started when they were older. Conclusions: HIV/HCV coinfected children receiving ART had slower CD4+ T cell recovery than HIV monoinfected children. HIV/HCV coinfection had no impact on pre-ART or long-term CD4 z scores. Early treatment of HIV/HCV coinfected children with ART should be encouraged.