Highly active antiretroviral therapy (HAART) is considered the most effective treatment for individuals with HIV-1 infection (Ahmad et al., 2011), although its effect on male reproductive function is still debatable. Epidemiological studies have revealed that the desire to raise children exists in about one-third of HIV patients and two-thirds of the patient population are usually overweight or obese, (Crum-Cianflone et al, 2008; Kushnir and Lewis, 2011). This study was designed to investigate the in vivo effects of HAART on some sperm functional parameters and the testicular oxidative status in lean and diet-induced obese (DIO) rats. Rats (males, 180-200g, n= 40) were assigned equally into 4 groups and treated orally for 16 weeks. Group I and II were the vehicle control groups that received 1.0 ml/kg/day distilled water by gavage for the latter 6 weeks. Group I served as the lean group fed with standard rat chow, Group II was the DIO group fed with rat chow supplemented with sucrose and condensed milk while Groups III and IV were lean and DIO groups respectively that were treated with HAART (antiretroviral drug combination of tenofovir, emtricitabine and efavirenz at a dose of, 17, 26 and 50mg/kg/day for the latter 6 weeks). At the end of the experimental period, animals were anaesthetized (160mg/kg pentobarbital i.p.) and the testis and epididymis removed. Sperm analysis was done on the sperm collected from the caudal epididymis while the testis was homogenized for antioxidant enzyme and lipid peroxidation assays. Values were expressed as mean ± S.E.M. compared by ANOVA. When the lean and DIO treated groups were compared with their respective control, results showed that HAART significantly decreased sperm motility (94.13±0.60% vs. 81.56±3.23%; 83.06±1.91% vs. 65.25±4.76%, p<0.05) and viability (97.00±2.44% vs. 81.86 ±2.26%; 89.29 ±1.43% vs. 78.43±2.08%, p<0.05). Testicular glutathione (50.17±4.18 vs. 18.83±1.85 μg/mg protein, p<0.05), catalase (143.5±14.61 vs. 112.80±10.94 μg/mg protein, p<0.05) and superoxide dismutase (7.92±0.16 vs. 6.23±0.23 μg/mg protein, p<0.05) were significantly decreased while Thiobarbituric acid reactive substances (TBARS) level (2.0±0.17 vs. 2.84±0.24 nmol/g tissue, p<0.05) was significantly increased only when the DIO HAART group was compared with DIO control group. Thus, the decrease in sperm qualities associated with HAART might be as a result of increased testicular oxidative stress pronounced in obese animals. These data implies that obesity is a confounding factor and interferes with the treatment regimens effectiveness.