The present work is undertaken to investigate the aerosol volume and mass size distribution, concentration of Particulate Matter (PM) and its source apportionment by using GRIMM spectrometer data in the city of Peshawar, Northern Pakistan. In Peshawar, the concentration of Particulate matter (PM2.5 and PM10) was noticed to increase day by day due to rapid urbanization and industrialization. The use of several transportation activities, construction of buildings, roads and overhead bridges has badly affected the atmosphere of this region. Positive Matrix Factorization (PMF) Model has been used to find out different sources of PM in Peshawar. The data were collected for twenty days in April 2011 for both morning and afternoon periods. It has been observed that the values of aerosol volume size distribution were almost high during morning and afternoon rush hours. The mean concentrations of PM10 and PM2.5 were determined to be 480 µg/m3 and 172 µg/m3, respectively. A reasonably significant correlation (R2 = 0.65) was also found between observed and expected PM mass. The PMF result revealed five (05) sources in Peshawar, which were re-suspended road/soil dust, vehicular, industrial, brick kiln emission and household combustion emission.