Mangosteen fruit has a high potential on the global fruit market, but some disorders, including translucent flesh, are major problems of fruit quality, limiting the marketability. The present study was conducted to compare physiological changes of reactive oxygen species (ROS), cellular lignification between translucent and normal aril, and elucidate the relation. Mangosteen fruits at purple peel color were collected from eastern Thailand during the middle of the rainy season of 2019. Translucent aril accumulated higher lignin content in the tissues, expressing firmer texture ten times higher than normal aril. Lignification was increased in translucent aril by 740% and 25% higher coniferyl alcohol dehydrogenase (CAD) and peroxidase (POD) activity, respectively, induced by high H2O2. Healthy aril performed higher activities of superoxide dismutase (SOD) (8.5 times) and ascorbate peroxidase (APX) (1.3 times) to those in translucent aril. Furthermore, the higher flavonoid content, ascorbic acid content, and antioxidant capacities detected in normal aril could significantly reduce oxidative stress. Although containing high antioxidant systems, healthy aril was found to accumulate higher malonaldehyde content (MDA). This study provides intensive evidence of oxidative stress and the defensive systems between normal and translucent tissues.