Aim/objectiveTo assess the common hematological abnormalities among HIV-antiretroviral therapy (ART) naïve clients attending an immune suppression syndrome (ISS) clinic at Mbarara Regional Referral Hospital (MRRH), southwestern Uganda.Patients and methodsThis was a cross-sectional study carried out during the months of March to August 2016 at the ISS clinic of MRRH. We collected approximately 4.0 mL of EDTA anticoagulated blood samples, which were assayed for complete blood count, CD4+ cell count and thin film examination. Correlation of the hematological abnormalities with CD4+ cell counts was done using correlation coefficient (r) and analysis of variance (F), and the p-value was set at ≤0.05.ResultsA total of 141 clients were enrolled. Of these, 67.38% (95/141) were anemic, 26.24% (40/141) had thrombocytopenia while 26.95% (38/141) had leucopenia. Of the 95 participants with anemia, 89.47% (85/95) presented with normocytic-normochromic anemia, 8.42% (8/95) with microcytic-hypochromic anemia and 2.11% (2/95) with macrocytic-hypochromic anemia. Anemia was not different across the several World Health Organization (WHO) stages of HIV infection disease progression (p>0.05). Statistically significant differences were present among participants with leucopenia (p<0.05). Also, leucopenia was more prevalent (11/38) among participants in WHO stage 4 of HIV infection. CD4+ cell counts correlated with thrombocytopenia (r=0.24, p<0.05) and leucopenia (r=0.15, p<0.05).ConclusionPeople living with HIV/AIDS (PLWHIV/AIDS) ought to be routinely monitored and treated for the occurrence of hematological abnormalities. Early initiation of ART can help to prevent some hematological abnormalities.