Urban expansion affects air quality, making it a critical concern in sustainable urban planning. Colombo and Kandy, major urban centres in Sri Lanka, face significant air pollution challenges due to vehicular emissions, urbanisation and industrial activities. This study employed cloud-based geospatial analysis to evaluate the impact of urban sprawl on air quality in Kandy and Colombo from 2001 to 2023. Data were sourced from NASA Land Processes Distributed Active Archive Centre (LP DAAC) at the USGS EROS Centre, including Terra & Aqua MAIAC Land Aerosol Optical Depth Daily 1 km (MCD19A2.061), Sentinel-5P Tropospheric Monitoring Instrument (TROPOMI) for analysing air quality and MODIS Land Cover Type Yearly Global 500 m (MCD12Q1.061) to assess urban growth. Analytical tools such as Google Earth Engine and ArcGIS Pro were used for time-series analysis and spatial visualisation of annual urban expansion, mean annual Aerosol Optical Depth (AOD) at 0.47 μm, and pollutant concentrations of Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Carbon Monoxide (CO) and Ozone (O3). The findings revealed a substantial relationship between urban growth and variations in air quality. Colombo urban area expanded from 159.39 km2 in 2001 to 199.63 km2 in 2023 (25.25% increase), predominantly towards the east and northeast. This urban expansion was accompanied by a sharp rise in mean AOD levels, from 9.64 to 18.45 (91.39% increase). In contrast, Kandy experienced slower urban growth, expanding from 8.27 km2 in 2001 to 8.77 km2 in 2023 (6.05% increase) towards the southwest, with mean AOD levels fluctuating from 7.05 to 11.48 (62.84% increase). Furthermore, air quality indicators such as NO2, SO2, CO and O3 have shown increasing trends in both cities since 2019. The rapid urbanisation in Colombo has a more significant adverse impact on air quality than the slower, steadier growth in Kandy, emphasising the necessity of developing city-specific mitigation to ensure sustainable urban development.