Thermoelectric studies of Cu2ZnSnS4 (CZTS) thin films deposited at different substrate temperatures by ultrasonic assisted chemical vapor deposition technique have been carried out. In order to identify the effect of compactness, crystallinity and formation of secondary phases (Cu-2 (-) S-x and SnS2) on the thermoelectric properties of CZTS thin films, the films were deposited at different substrate temperatures. Detailed analysis of temperature dependent electrical resistivity (rho) and Seebeck coefficient (S) have been carried out. Significant enhancement in the value of thermoelectric power factor (S-2/rho) is achieved in CZTS film deposited at 375 degrees C substrate temperature, which is correlated to the compactness of thin films, improved crystallinity and presence of metallic secondary phase. Furthermore, Surface topography and surface potential studies also carried out to study the roughness and distribution of interfaces between CZTS and secondary phases (Cu2 - S-x and SnS2) in CZTS thin films.