Various studies have indicated that peptic ulcers occurring during the course of diabetic state are more severe and often associated with complications such as gastrointestinal bleeding. This study is an attempt to understand the pathogenesis of indomethacin-induced gastric ulcers occurring during the diabetic state using suitable markers and its amelioration by quercetin and coenzyme Q10 (CoQ10). In this study, diabetic rats showed an increase in the gastric mucosal levels of Molandialdehyde (MDA), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), tumor necrosis factor (TNF-α), BAX and p53 and a decrease in the activities of superoxide dismutase (SOD) as compared to normal control (non-diabetic) rats. There was an increase in gastric ulcer index and gastric ulcer lesions in diabetic gastric mucosa when compared to the normal control group. Pre-treatment with quercetin and\or CoQ10 to normal groups or diabetic groups which treated by indomethacin caused a significant decrease in gastric ulcer index, MDA, iNOS, IL-6, TNF-α, BAX and p53 with concomitant increase in SOD activity when compared with normal and diabetic rats treated with indomethacin alone. So quercetin and CoQ10 are effective in protection against indomethacin-induced gastric ulcers in normal and diabetic rats. Our findings could bring new hope for a novel modality of gastric ulcer treatment.