Co-infection with HTLV-1 reaches 20% among patients infected by HIV-1 in Bahia, Brazil. To evaluate its impact on survival, we conducted a retrospective, case-control study involving 198 patients (63 cases). Co-infection was associated with parenteral exposure (P = 0.0001) and female sex (P = 0.02). Co-infected patients had a shorter mean survival (1849 days) than controls (2430 days, P = 0.001), regardless of sex or baseline CD4 cell count. In Bahia, Brazil, co-infection with HIV-1 and HTLV-1 is associated with a shorter survival time.