Background Air pollution poses a significant public health threat, in urban cities where worsening air quality is linked to rising respiratory morbidity. This study explores the association between Air Quality Index (AQI) levels and emergency department (ED) visits for acute respiratory illness (ARI) in a tertiary care hospital in Mumbai.Methods A surveillance record-based study was conducted over 1036 days (March 2020–December 2022). Daily ED visits under three speciality departments were recorded. Outcome measures included the number of ARI cases, nebulization need, hospital admissions, and ventilatory support. AQI data were obtained and categorised into standard ranges from the CPCB portal. Statistical analysis was performed using negative binomial regression in STATA v15.1.Results During the study period, the median AQI was 83 (IQR: 58–152) and median daily ED visits for ARI were 16 (IQR: 11–20). After adjustment for the confounding effect of seasons, compared to good AQI days, satisfactory AQI was linked to a 15% higher incidence of ARI cases (IRR: 1.15; p < 0.001). In addition, there was a 2.13 times higher likelihood of requiring nebulization (IRR: 2.13; p < 0.001), a 1.26 times higher risk of hospital admission (IRR: 1.26; p < 0.001), and a two times higher NIV requirement (IRR: 2.00; p < 0.001). A significantly higher need of invasive ventilation (IRR: 1.49; p = 0.013) was noted for the poor and very poor AQI category.Conclusion Poor air quality worsens respiratory health and increases emergency care demands, highlighting focused pollution control and planned hospital preparedness in response to air pollution effect in urban areas.