Modification of poly(ethylene terephthalate) (PET) fabric with low temperature oxygen plasma has been studied. Prior to the plasma modification, the fabric was treated with a strongly-interacting solvent, dimethylformamide (DMF). The effect of the prior DMF treatment on the subsequent plasma treatment was examined. The plasma-treated sample was characterized by X-ray photoelectron spectroscopy and viewed under a scanning electron microscope. Also wettability and loss in weight after plasma treatment were measured. The oxidative functionalization, surface roughness, and wettability are significantly larger for the sample which has received DMF treatment prior to the plasma treatment than that treated solely with the plasma. Furthermore, DMF-treated PET is much more subjected to etching after plasma treatment than the DMF-untreated sample and hence the weight loss of the former sample is larger than that of the latter one. DMF followed by plasma treatment leads to significant effect on the surface morphology. DMF-induced plastisization in PET causes a marked influence on the subsequent plasma modification.