Chemical characterization and source apportionment of PM 10 and PM 2.5 were carried out for two different elevations (lower elevation (LE) ~ 5–10 m and higher elevation (HE) ~ 30–45 m) at four different locations representing urban background, city center, upwind, and downwind of the Delhi city during January 2017–March 2017. The 24-h average PM 10 and PM 2.5 concentrations were varied between 135.2–258.7 and 79.3–120.9 µg/m 3 , respectively. The average PM 10 and PM 2.5 concentrations were found significantly higher at LE than HE. The PM samples were analyzed for ions, elements and carbonaceous matter (EC/OC), and their concentrations (except S, V, As, Ni, Sb, Sr, Ga, elements associated with industrial combustion activities, and NO 3 − , attributed to high nitrate formation potential at HE) were observed higher in LE than HE at all the study locations. The chemical mass balance model was applied to quantify the source contributions to PM 10 and PM 2.5 mass at two different elevations. Model identified vehicular emission (diesel, PM 10  ~ 8.8–21.7% and PM 2.5  ~ 10.5–24.4% and gasoline, PM 10  ~ 4.8–15.6% and PM 2.5  ~ 6.7–14.8%), industrial residual oil combustion (PM 10  ~ 8.8–23.5% and PM 2.5  ~ 3.2–10.4%), road dust (PM 10  ~ 13.6–22.3% and PM 2.5  ~ 8.8–17.8%), soil dust (PM 10  ~ 33.8–41.1% and PM 2.5  ~ 5.8–8.3%), secondary nitrate (PM 10  ~ 6.1–16.2% and PM 2.5  ~ 13.4–20.2%), secondary sulfate (PM 10  ~ 7.1–12.3% and PM 2.5  ~ 10.6–16.7%), and biomass burning (PM 10  ~ 6.8–21.8% and PM 2.5  ~ 4.9–38.7%) as the main sources of PM 10 and PM 2.5 mass at both the elevations at all the study sites. The contribution of industrial residual oil combustion, vehicular emission, and secondary nitrate to PM 10 and PM 2.5 mass was found relatively higher in HE than LE. Results also revealed that biomass burning contributed significantly to PM pollution in the outskirts of Delhi than inside the city. Further, potential source contribution function analysis revealed that there may not be a long-range transport of PM emitted from biomass burning in the upwind region of Delhi during the study period. Shifting to Indian BS VI vehicles and fuel, switching to cleaner fuel in slum households, strict compliance on industries, and regular vacuum cleaning of roads will reduce the severe air quality problem in Delhi.