This study apportions sources of carbonaceous aerosols using isotopic characteristics of total carbon (TC) and elemental carbon (EC) in PM10 aerosols using filter-based CTO-375 method for pre-monsoon (summer), post-monsoon, and winter (2019–2021) over Hyderabad, India. Highest secondary organic carbon, SOC (primary organic carbon, POC) of 13.78 ± 10.25 (7.87 ± 2.48) μg/m3 was during post-monsoon 2020 (2019), while lowest was 8.90 ± 5.55 (4.18 ± 0.92) μg/m3 during pre-monsoon 2021 (post-monsoon 2020), respectively. Average effective carbon ratio (ECR) > 1 indicates dominance of light scattering aerosols during pre-monsoon and post-monsoon. δ13CTC and δ13CEC varied from – 28.1 to – 24.7 ‰ (avg. – 26.5 ± 0.7) and - 32.5 to – 24.6 ‰ (avg. – 27.4 ± 1.1), indicating contribution from C3 plant burning and liquid fuel combustion. Positive value of δ13COC – δ13CEC and heavier δ13CTC, along with gradual enrichment in δ13CTC and δ13CEC from December 2020 to March 2021, suggested photochemical aging of carbonaceous aerosols. Lighter δ13CTC and OC/EC > 4 for all seasons indicates dominance of biomass burning (wood and crop residue burning), photochemical oxidation and secondary organic aerosol (SOA) formation. The tropical study experiences dominance of lighter δ13CEC compared to subtropical, high latitude regions.