Mosquitoes of the family Culicidae are distributed worldwide and comprise about 3500 species. The diversity of the mosquito species varies among different geographical regions of the world. Assam is situated in the subtropical region with fluctuation in temperature in different seasons and heavy rainfall occurs in a particular period. So, mosquito vector surveys were conducted in different seasons to identify the distribution of different species of mosquito and to find out their seasonal patterns of abundance in the city of Guwahati situated in the south bank of the river Brahmaputra. Mosquito larvae were collected in the monsoon and the autumn season (July 2012 to October 2012) from different breeding sites including seven localities in the city using glass sucking pipette. pH and salinity of the water of the breeding sites were also measured. Altogether, seven mosquito species belonging to four genera namely Anopheles, Aedes, Mansonia and Culex were collected out of which the three genus Anopheles, Culex and Aedes are medically important vectors of several human diseases including, malaria, dengue, yellow fever, filariasis, Japanese encephalitis, chikungunya, etc. which are prevalent in this part of the region. The site selection for the present survey is mainly based on population density, water stagnation and unplanned drainage with poor garbage management sites of the Guwahati City of India. Most of the study sites were enriched with organic matter, sewage, green algae, short herbs, and upright vegetation. From the seven breeding sites, a total of 1557 mosquito larvae were collected. Among these, mosquito species, Culex quinquefasciatus was found to be most abundant species in the city comprising 29.92% (466 larvae) which was followed by Culex tritaeniorhynchus (26.08%, 406 larvae), Aedes aegypti (14.96%, 233 larvae), Anopheles minimus (12.01%, 187 larvae) and Aedes albopictus (6.29% , 98 larvae) of the total larvae collection.