Background: The aim of the study is to compare the incidence of sudden sensorineural hearing loss (SSNHL) in Northern and Southern Taiwan, areas with different levels of air pollution. Methods: This was a retrospective, cross‑sectional, 15‑year nationwide study of SSNHL diagnoses between 2000 and 2015 in Taiwan National Health Insurance Research Database. Results: In total, 12,497 patients were included, 5584 in Northern Taiwan and 2532 in Southern Taiwan. In Northern and Southern Taiwan, the mean patients’ age was 50.94 ± 16.62 and 50.70 ± 15.86 years, respectively; males (53.56% vs. 53.48%) were more frequently diagnosed than females (46.44% vs. 46.52%). The crude incidence was 41.13/100,000 and 49.45/100,000 in Northern and Southern Taiwan. The increasing trend was significantly higher in Southern than in Northern Taiwan. The maximal difference between Northern and Southern Taiwan, 44.31 versus 77.01/100,000 people/year, occurred in 2012. Mean particulate matter (PM2.5) annual concentration steadily decreased from 25.5 μg/m³ in 2010 to 19.20 μg/m³ in 2015 in Northern Taiwan, 37.10 μg/m³ in 2010 to 26.50 μg/m³ in 2015 in Southern Taiwan, Tainan City area, and 38.20 μg/m³ in 2010 to 25.10 μg/m³ in 2015 in Southern Taiwan, Kaohsiung City area. Cumulative PM2.5 exposure (PM2.5‑year) from 2000 to 2015 was 441.1 μg/m³ × year in Northern Taiwan, 563.3 μg/m³ × year in Southern Taiwan – Tainan City area, and 684.3 μg/m³ × year in Southern Taiwan – Kaohsiung City area. Conclusion: SSNHL incidence increased from 2000 to 2015 and was higher in Southern than in Northern Taiwan. Cumulative PM2.5 exposure was higher in Southern than in Northern Taiwan. The relationship between cumulative PM2.5 exposure and SSNHL pathogenesis needs further investigation.