Air pollution from traffic sources is considered to be a major environmental challenge the burgeoning metropolitan cities of the developing nations confront today.Like other mega-cities in the developing countries, air pollution has emerged as a serious problem in the Dhaka city. Dhaka, one of the largest mega cities of the world, is also faced with serious air pollution problem due to rapid growth of vehicles in recent times. This study mainly concentrated on two issues of air quality in Dhaka city and contribution of vehicles emission. The maximum and minimum SO2 and CO concentration is 24 ppb & 3 ppb and 0.5 ppb & 0.2ppm respectively which remain below acceptable limit (30ppb& 35ppb). The major contribution of this air pollution in Dhaka is coming from the complex vehicles fleet. It reveals from this study that a total of 1213.76 ton of various kinds of pollutants emit from the vehicles fleet in the Dhaka city every day. The tests revealed that old diesel run vehicles are the worst polluters that contribute mostly in the rise of particulate matter in the ambient air of the city.