The present study aims to investigate the adverse effects of plant growth regulators : gibberellic acid (GA3) and indoleacetic acid (IAA) on testicular functions in rats, and extends to investigate the possible protective role of grape seed extract, proanthocyanidin (PAC). Male rats were divided into six groups; control group, PAC, GA3, IAA, GA3 + PAC and IAA + PAC groups. The data showed that GA3 and IAA caused significant increase in total lipids, total cholesterol, triglycerides, phospholipids and low-density-lipoprotein cholesterol in the serum, concomitant with a significant decrease in high-density-lipoprotein cholesterol, total protein, and testosterone levels. In addition, there was significant decrease in the activity of alkaline phosphatase, acid phosphatase, and gamma-glutamyl transferase. A significant decrease was detected also in epididymyal fructose along with a significant reduction in sperm count. Testicular lipid peroxidation product and hydrogen peroxide (H2O2) levels were significantly increased. Meanwhile, the total antioxidant capacity, glutathione, sulphahydryl group content, as well as superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase activity were significantly decreased. Moreover, there were a number of histopathological testicular changes including Leydig's cell degeneration, reduction in seminiferous tubule and necrotic symptoms and sperm degeneration in both GA3- and IAA-treated rats. However, an obvious recovery of all the above biochemical and histological testicular disorders was detected when PAC seed extract was supplemented to rats administered with GA3 or IAA indicating its protective effect. Therefore it was concluded that supplementation with PAC had ameliorative effects on those adverse effects of the mentioned plant growth regulators through its natural antioxidant properties.