Air pollution has been shown to significantly impact human health including cancer. Gastric and upper aerodigestive tract (UADT) cancers are common and increased risk has been associated with smoking and occupational exposures. However, the association with air pollution remains unclear. We pooled European subcohorts (N = 287,576 participants for gastric and N = 297,406 for UADT analyses) and investigated the association between residential exposure to fine particles (PM_2.5), nitrogen dioxide (NO₂), black carbon (BC) and ozone in the warm season (O_3w) with gastric and UADT cancer. We applied Cox proportional hazards models adjusting for potential confounders at the individual and area-level. During 5,305,133 and 5,434,843 person-years, 872 gastric and 1139 UADT incident cancer cases were observed, respectively. For gastric cancer, we found no association with PM_2.5, NO₂ and BC while for UADT the hazard ratios (95% confidence interval) were 1.15 (95% CI: 1.00–1.33) per 5 μg/m³ increase in PM_2.5, 1.19 (1.08–1.30) per 10 μg/m³ increase in NO₂, 1.14 (1.04–1.26) per 0.5 × 10⁻⁵ m⁻¹ increase in BC and 0.81 (0.72–0.92) per 10 μg/m³ increase in O_3w. We found no association between long-term ambient air pollution exposure and incidence of gastric cancer, while for long-term exposure to PM_2.5, NO₂ and BC increased incidence of UADT cancer was observed.