Polyester fibers (PES) are the most consumed textile fibers due to their low water absorption; non-ionic character and high crystallinity. However, due to their chemical structure, the chemical interactions between polyester, finishing products, and dyes are quite challenging. We report on the use of ozone to modify the surface of polyester fibers with the goal of improving the interaction of the modified surface with finishing compounds and dyes. We used C.I. Disperse Yellow 211 to dye ozone-treated polyester fabrics and evaluated the effects of ozone treatment using FTIR-ATR, Raman spectroscopy, SEM imaging, rubbing tests, and capillarity measurements. We evaluated the dyeing performance via color analysis, and determined the dyeing kinetics. Experimental results indicate that the modification of polyester fabrics with ozone is a feasible pre-treatment that improves dyeing efficiency allowing better solidity of color and a decrease in the amount of dye required.