Body of Abstract: Plants can uptake, accumulate, and metabolize persistent organic pollutants from the environment, a process referred to as phytoremediation. Polychlorinated biphenyls (PCBs) are toxic contaminants that have been largely dispersed in the environment for more than 50 years. The use of PCBs was largely restricted in 1979 because they were a potential hazard to animals and humans. Due to their high hydrophobicity and chemical stability, phytoremediation of PCBs, is known to be a slow process. The main objective of this study is to understand the effects of the plant safener(fenclorim), on the metabolism of PCB-11 in the model plant Arabidopsis thaliana at physiological and molecular levels. Safeners are chemicals known to protect plants against the toxic effect of herbicides and they are believed to act through the induction of detoxifying enzymes, such as glutathione S-transferases (GSTs) and cytochrome P-450 monooxygenases (CYP). A. thaliana plants were exposed to PCB-11 and the effect of the safener, fenclorim was investigated through toxicity tests and gene expression analysis targeting a suite of GST and CYP genes known to be involved in the metabolism of xenobiotic compounds. A.thaliana plants exposed to PCB had a reduced biomass compared to control plants. However, plants treated with PCB and fenclorim had increased biomass compared to plants exposed to PCB alone. Gene expression analysis showed that the expression of specific genes involved in the metabolism of xenobiotics was induced by fenclorim treatment. The following genes CYP71OA1, 8CYP1D8, CYP81F2, CYP71B15, GSTU 24, and GSTU 25 showed a statistical increase in the level of expression. Fenclorim can induce the expression of specific genes involved in xenobiotic response in A.thaliana, which can lead to increased biomass in plants exposed to PCB-11. These findings suggest that fenclorim may have potential applications in the phytoremediation of PCB-contaminated soils.