Background: HTLV-1 or 2 co-infection in individuals infected with HIV-1 can lead to increased morbidity. The shared routes of transmission of HTLV with HIV-1 may increase the prevalence of HTLV among HIV-1 infected population and subsequently affect patient's management. Methods: Sera were collected from 144 HIV-1 infected individuals attending the highly active anti-retroviral therapy (HAART) clinic of the University of Ilorin Teaching Hospital between the months of May and August 2016. Sera were tested for anti-HTLV IgM and IgG antibodies to HTLV-1&2 using the sandwich enzyme-linked immunosorbent assay. Results: Out of the 144 participants tested, 47 (32.6%) and 37 (25.7%) were positive for HTLV IgG and IgM respectively. Twenty-one participants (14.6%) had both IgG and IgM antibodies to HTLV-1&2. Ten individuals were anti-retroviral drug naïve out of which, four and six were positive to anti-HTLV IgG and IgM respectively. Conclusion: Findings from this study revealed that there is high sero-prevalence of HTLV IgG and IgM antibodies among HIV-1 sero-positive individuals in Ilorin. The high rate of co-infection supports routine screening for HTLV-1/2 co-infection among HIV-1 infected individuals in Ilorin, Nigeria so that the purpose of HAART treatment and monitoring of patients to prevent progression to AIDS will not be aborted.