Background: Coexistence of malaria with HIV in Sub-Saharan African and its attendant high morbidity and mortality could be a threat that can reverse the gains of ART in HIV-infected children. Aim: This study aims to determine the impact of ART on immunity and malaria among febrile HIV-infected children seen in UDUTH, Sokoto, Nigeria. Materials and Methods: A cross-sectional study was conducted among HIV-infected children presenting with fever at the Paediatric ART and other Paediatric Outpatient Clinics in the hospital between May and October 2016. Blood film for malaria parasite, packed cell volume, random blood sugar, retroviral test and CD4⁺Tcell count were done for the participants. Data were analyzed using the IBM SPSS version 23.0 computer statistical software package. A p-value < 0.05 was considered as significant. Results: A total of 100 febrile HIV-infected children on ART, and 40 febrile newly diagnosed HIV-infected children not on ART were recruited. The prevalence of malaria among the febrile HIV-infected children on ART was 60% (60/100) compared to 100% (40/40) among those not on ART (χ²=25.6, p < 0.001). Among the 60 HIV-infected children on ART who had malaria, 12(20.0%) had severe malaria compared to 34 (85.0%) among the 40 that were not on ART (χ²=25.6, p < 0.001). The mean CD4⁺T cells count was 403 ± 168cells/μl among the HIV infected children on ART compared with 194 ± 67cells/μl in the treatment naïve patients, and the difference was statistically significant (p < 0.001). Although, the CD4⁺T-lymphocyte level correlates negatively with malaria parasite density among the HIV-infected children, it was not statistically significant (r = -0.082, p = 0.33). Conclusion: ART boosted immunity and reduced malaria prevalence and severity in febrile HIV-infected children. Efforts should be intensified towards early diagnosis and prompt commencement of ART in HIV-infected children.