We analyzed hourly measured fine particle (PM2.5) concentrations for 2016 at the five U.S. Diplomatic Missions in India: New Delhi, Mumbai, Chennai, Hyderabad, and Kolkata. We calculated monthly mean concentrations and found that the highest generally occur in November-February and the lowest in June–September. The highest monthly mean concentrations are ~ 4–10 times greater than the lowest. Night-time concentrations are generally greater than daytime concentrations except in Chennai where day and night-time concentrations are similar. Daily mean concentrations exceeded the daily Indian National Ambient Air Quality Standard of 60 μg m−3 on 49–219 days during 2016 at these sites. The annual mean PM2.5 concentration ranged between 41–123 μg m−3 across the sites and exceeded the annual Indian National Ambient Air Quality Standard of 40 μg m−3. A comparison of the Community Multiscale Air Quality (CMAQv5.3.2) model predictions with measured data suggest that the model can reproduce the monthly variation in measured data but tends to under-predict the higher measured concentrations in November-February and over-predicts the lower measured concentrations in June–September. The model overestimates monthly and diurnal mean concentrations at Kolkata for all months and hours.