Introduction: Among opportunistic pathogens associated with acquired immunodeficiency syndrome (AIDS), Mycobacterium tuberculosis is distinguished by its relative virulence and potential for person-to-person transmission. Oxidative stress is associated with TB infection with a high level in patients with HIV-TB co-infection. However, the comparative level of oxidative stress in HIV patients on highly active antiretroviral therapy (HAART) and naïve (untreated) HIV patients is not clear. Methodology: This study is aimed to determine the level of oxidative stress and haematological parameters in HIV patients (naïve), HIV patients undergoing HAART, and HIV-TB co-infected patients. In total, 100 consenting subjects were recruited from the AIDS Prevention Iniative in Nigeria (APIN) Clinic. For controls, normal male healthy volunteers were recruited from the blood donor clinic and females from the APIN clinic staff members, both of the Lagos University Teaching Hospital. Measurements of antioxidant enzyme activity and lipid peroxidation were performed according to standard procedures. Haematological parameters were determined using a fully automated hematology analyzer. Results: Red blood cells significantly decreased (P≤0.001) in all patients when compared with control subjects. The lipid peroxidation (MDA) was significantly high (P≤0.05) in naive patients when compared to HIV patients on HAART. The decrease in the levels of GSH in both naive and HIV-TB co-infected patients (P≤0.001) and HIV patients on HAART (P<0.05) were significant when compared to control patients. Conclusion: There is lower antioxidant level and higher MDA in naive and HIV-TB co-infected patients as compared to HIV patients on HAART and the seronegative patients.