Chemical mass balance (CMB 8.2), a source apportionment model, was employed to identify the sources influencing the measured PM2.5 levels at an industrialized urban and a coastal rural site located in Corpus Christi, Texas. A speciated PM2.5 dataset consisting of 110 common sampling days with 25 key species, including elements, water soluble ions, organic and elemental carbon measured from 2003 to 2005, was used in this analysis. Based on the local and regional emissions characteristics, thirteen generic source profiles were selected from US EPA’s SPECIATE library for the CMB model application. Secondary sulfate was the major contributor at both sites with average concentrations of 3.45 μg/m3 (42% of the apportioned mass) and 3.06 μg/m3 (37%), respectively. Secondary organic aerosols were observed to be higher at the urban site (1.62 μg/m3) than at the rural one (1.07 μg/m3). Due to its location being closer to the Gulf of Mexico, the influence of marine aerosols was higher at the coastal rural site (1.15 μg/m3) than at the urban one (0.37 μg/m3). Unique sources, including the petroleum industry and industrial manufacturing, were found to influence the measured PM2.5 levels at the industrialized urban site, with average apportioned concentrations of 0.17 μg/m3 and 0.02 μg/m3, respectively. The annual average PM2.5 concentrations showed a gradual increase in the secondary components, including sulfates and organic aerosols at both sites during the study period.