Evidence on the relationship between gaseous air pollutants and male reproductive hormones remains limited. This study examined the associations of ambient CO, NO2, SO2, and O3 exposure with serum reproductive hormone profiles among men seeking assisted reproduction. We included 3284 men from an assisted reproduction cohort in Anhui, China. Individual exposures to CO, NO2, SO2, and O3 were estimated for 0-90, 0-180, 181-360, and 0-360 days before hormone measurement. Serum FSH, LH, PRL, T, E2, and hormone ratios were assessed. Linear regression, quintile-based trend analyses, restricted cubic spline models, and stratified analyses were performed with adjustment for demographic, lifestyle, reproductive, meteorological, and environmental covariates. SO2 exposure was associated with lower levels of T, T/LH, and T/E2 across all four exposure windows, whereas O3 exposure was associated with higher levels of these androgen-related indicators. Quintile-based trend analyses further supported exposure-response associations between SO2 and O3 exposure and male reproductive hormone levels. Restricted cubic spline and piecewise regression analyses suggested a threshold-like nonlinear relationship between SO2 exposure and T, with the inverse association mainly observed within the low-to-moderate exposure range. In contrast, the findings for CO and NO2 were less frequent and showed limited stability. Ambient SO2 and O3 exposures were associated with altered male reproductive hormone profiles among men seeking assisted reproduction. Further studies incorporating semen quality, fertility outcomes, and mechanistic biomarkers are warranted.