Indian cities are the hotspots of human population with population densities as high as 66,135 persons/sq km and are hence emerging as one of the significant CO2 emitters on par with cities of the developed nations. In this regard, quantification of Indian urban CO2 emissions at a finer resolution of space and time is becoming a crucial prerequisite for the implementation of India's National Action Plan on Climate Change. This paper presents the quantification of CO2 emissions of Chennai city at a fine spatial (1 km × 1 km) and temporal (diurnal, weekday-weekend, seasonal) resolution. In the present study, data sets of residential, industrial, commercial, traffic and waste management sectors were considered and bottom up approach was used for quantifying the CO2 emissions. Results indicated that the total annual CO2 emission of Chennai city was 2.12 Mt. Domestic (45.7%) and transportation (29.7%) sectors were identified as the larger CO2 emitters followed by power generation sector (17.4%). The average grid wise anthropogenic CO2 emission was found to be 0.01 ± 0.02 Mt/yr with peak CO2 emissions observed from the grids with point sources and minimal CO2 emissions from the grids overlaying on the urban forest of the city. The average per capita CO2 emission of Chennai was found to be 0.45 tons/yr which is less than the national per capita CO2 emission of 1.6 tons/year. The estimated CO2 fluxes due to anthropogenic emissions were in the range of 0-8.5 × 10-6 kg/m2/s with an average flux of 0.36 × 10-6 kg/m2/s. CO2 emissions during weekdays and weekends in summer season (5862.6 and 6235.58 tons/day) were slightly higher than in winter season (5540.8 and 5929.6 tons/day). Grids overlaying on commercial and residential zones showed higher CO2 emissions during morning (07:00-10:00 AM) and evening rush hours (07:00-09:00 PM) of a day. © 2015 Elsevier Ltd.