PURPOSE: Human T-lymphotropic virus type 1 (HTLV-1) is an endemic virus in Latin America that is directly linked to adult T-cell leukemia/lymphoma (ATL). Previous studies have suggested an oncogenic role of HTLV-1 in non-ATL neoplasms and have found higher mortality in HTLV-1 carriers without ATL. METHODS: In this retrospective cohort study, HTLV-1 carriers were identified through screening at a tertiary cancer center between 2006 and 2019. We compared the overall survival (OS) outcomes of patients with ATL with those with other solid or hematologic malignancies by sex stratification. RESULTS: We identified 1,934 HTLV-1 carriers diagnosed with cancer. The median age at diagnosis was 62 (range 20-114) years, 76% were female, 60% had no or elementary school education, and 50% were born in the Andean highlands. The most common non-ATL neoplasm was cervical cancer (50%) among females and non-ATL non-Hodgkin lymphoma (26%) among males. With a median follow-up of 66 months, the 5-year OS of HTLV-1 carriers with non-ATL neoplasms (26%-47% for females and 22%-34% for males) was inferior to those reported in the general population. As expected, patients with ATL had a worse prognosis (5-year OS: 10% for females and 8% for males). CONCLUSION: HTLV-1 carriers with cancer were middle age and from underprivileged settings, suggesting an undetected transmission among vulnerable populations, especially females. Survival estimates of HTLV-1 carriers with non-ATL neoplasms were lower than the regional outcomes. Future research should ascertain how the biology of HTLV-1 and health care disparities affect the outcomes of HTLV-1 carriers, as well as determine the burden of HTLV-1 infection in the cancer population to recommend screening in the outpatient setting of endemic regions.