Accumulation of overtraining/OT volume, in the long run can lead to decreased performance called overtraining syndrome (OTS). Oxidative stress, an imbalance state of endogenous antioxidants and free radicals, is closely related to pathophysiology of OTS and in the long run can cause cardiovascular disorders. Some research shows that oxidative stress can be inhibited through antioxidants supplementation. Hibiscus Sabdariffa Linn. (H. sabdariffa) is a plant that contains high antioxidants. This study aims to explore the effect of OT on oxidative stress level in rat's cardiac tissue and the effect of H. Sabdariffa supplementation to the level of oxidative stress in OT rats. The study was an experimental study using 25 adult Wistar rats, 8-10 weeks, 290-390 gr, randomized into five groups: Control (C), Control + Hibiscus (C-Hib), Aerobic Exercise (A), Overtraining (OT) and Overtraining + Hibiscus (OT-Hib). Dosage of H. sabdariffa given: 500 mg / kg / day. Aerobic physical exercise was given 2 x/wk, 10 min, 12 m/min, lasted for 11 wks. Overtraining protocols was given 5x/wk with increasing frequency and decreasing recovery time between sessions for 11 wks. Calculated levels of MDA, SOD and GSH using spectrophotometry and Nox2 using ELISA at the end of Week 11. The result showed that overtraining induces an oxidative stress condition in the rat's cardiac tissue characterized by higher MDA levels than aerobic and control rats, and lower GSH levels than aerobic rats. The administration of H. sabdariffa may induce oxidative stress reduction in overtraining rat's cardiac tissue, characterized by lower MDA levels and higher GSH levels in overtraining rats given H. sabdariffa compared to overtraining rats.