Trace elements contribute a small fraction to fine-mode aerosols as compared to the other chemical species (organic & inorganic) and affect the ambient air quality and human health. In this paper, we report the inter-annual and seasonal concentrations, and sources of trace elements in PM_2.5 over Delhi, India based on long-term analysis (2013–2021). In all the PM_2.5 samples 19 trace elements were extracted: Na, Mg, Ca, Mn, Al, Fe, Ti, Cu, Zn, Cr, Ni, As, Mo, Cl, P, S, K, Pb, and Br. The total annual mean concentration (∑El in PM_2.5) of trace elements was 17.49±3.13 µg m^-3 which is accounted for 13.9% of PM_2.5 mass concentration. Enrichment factor (EF) and IMPROVE model analysis indicate the seasonal abundance of mineral/soil dust (Fe, Al, Ti, Na, Ca, and Mg) at the sampling site of Delhi, India. During the sampling period, the highest loading of trace elements was recorded in 2015 (19% of PM_2.5) and the lowest in 2020 (9% of PM_2.5) due to restricted activities during covid-19 lockdown/unlock periods. Four major sources of trace elements (in PM_2.5) were extracted by principal component analysis as crustal/soil dust, vehicular traffic/industrial emissions, combustion (solid+fossil fuels), and sodium magnesium salts in Delhi. This long-term study on the elemental composition of PM_2.5 will be useful for policymakers in mitigating ambient air quality and improving human health.