A comprehensive study was made on biotransformation of p-coumaric acid and 2,4-dichlorophenoxyacetic acid by an Azotobacter sp. strain SSB81. The strain was able to tolerate a high amount of both the phenolic acids and p-coumaric acid degraded maximum (50%) than 2,4-D (29%) after five days of incubation. The intermediate products during transformation have been identified and quantified using UV-Vis and LC-MS/MS analysis. Para-coumaric acid was degraded via p-hydroxybenzoic acid and protocatechuic acid, a non-oxidative pathway whereas 2,4-D via 4-chlorophenoxyacetic acid, 4-chlorophenol and 4-chlorocatechol, an oxidative pathway. The results suggest that SSB81 developed both the oxidative and non-oxidative pathway to degrade the soil accumulated phenolic acids. Thus, Azotobacter provides an advantage to reduce the toxic level of soil accumulated phenolic acids in addition to increase the soil fertility. (C) 2012 Elsevier Ltd. All rights reserved.