Hepatitis C virus (HCV) and human T-lymphotropic virus type 1 (HTLV-1) coinfection occurs in many regions. However, few studies have focused on the natural history of HCV-induced liver disease in coinfected patients. To describe the clinical, epidemiological, and histopathological aspects of HTLV-1/HCV coinfection in Brazil. A cross-sectional study with 23 patients coinfected with HCV/HTLV. The control groups consisted of 21 patients monoinfected with HCV and 20 patients monoinfected with HTLV-1. The cytokine profiles (Th1 and Th2 cell responses), clinical, laboratory features, and histopathological aspects were examined. The control group for cytokine analysis validation consisted of patients monoinfected with HTLV, and a fourth group consisted of healthy blood donors. No anthropometric differences present between the three infected groups. We observed higher serum concentrations of IFN-γ in patients coinfected with HCV/HTLV-1 than those in HCV monoinfected patients. The HCV/HTLV-1 coinfected group also exhibited a higher degree of liver steatosis than the HCV monoinfected patients. Results suggest that HCV/HTLV-1 coinfection may result in a different pattern of HCV infection due to the immunologic disorders likely associated with HTLV-1, but there is no clear evidence of the HTLV role in the natural history of HCV infection.