HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic demyelinating and disabling syndrome caused by human T lymphotropic virus 1 (HTLV-1). Although the pathogenic mechanisms that lead to HAM/TSP outcome have not been elucidated, genetic and immunological factors may be involved in the myelopathy occurrence. This study aimed to compare cytokines, chemokines, and nitric oxide (NO) levels in asymptomatic and HAM/TSP HTLV-1-infected patients. The study group consisted of 21 HAM/TSP and 48 asymptomatic HTLV-1 patients. Chemokines (CCL5, CCL2, CXCL8, CXCL9, and CXCL10) and cytokines [IL-2, interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), IL-4, IL-6, and IL-10] were measured using cytometric bead array, whereas NO production was measured after reaction of supernatants with nitrate reduction solution. CXCL9 and CXCL10 chemokines levels were found to be higher in the HAM/TSP group. CXCL9 was also strongly correlated with CXCL10 and both CXCL9 and CXCL10 were moderately correlated with CCL2 and CCL5 levels, in both HAM/TSP and asymptomatic groups. There was no significant difference related to NO, IL-4, IL-6, and IL-10 levels between the clinical groups but TNF-α and IFN-γ levels were increased in HAM/TSP patients. Thus, factors such as CXCL9, CXCL10, TNF-α, and IFN-γ could be good prognostic biomarker candidates, and further studies may help to clarify their association with HAM/TSP immunopathogenesis.