The protective effect and mechanism of cuminaldehyde, the active ingredient of cumin, was investigated in the indomethacin-induced gastric ulcer rat model. To this end, a control group (CK), indomethacin model group (Model), omeprazole positive control group (Positive), as well as cuminaldehyde low (CUM2), medium (CUM4), and high (CUM6) dose groups were employed, with six mice per group. Indomethacin was continuously administered over 7 days in order to establish the gastric ulcer rat model. The morphology, gastric ulcer index, pepsin activity, and antioxidant properties of gastric tissue were evaluated. Higher cuminaldehyde doses decreased the number of stripe-like ulcers and bleeding spots in gastric tissue. Further, edema and erosion were alleviated, the arrangement of glands tended to be orderly, and inflammatory cell infiltration was suppressed. The ulcer index and pepsin activity gradually decreased in a dose-dependent manner (P<0.01), whereas the ulcer inhibition rate increased. The highest ulcer inhibition rate was observed in the CUM6 group (58.48%). SOD and CAT activity as well as the GSH and NO content in gastric tissue increased to varying degrees, whereas MDA levels decreased under cuminaldehyde treatment (P<0.05 or P<0.01). Serum TNF-α and IL-1β levels, as well as MPO activity decreased, whereas IL-10 and PGE2 levels increased. In conclusion, cuminaldehyde could significantly reduce the size of ulcers and suppress pepsin activity while improving antioxidant and anti-inflammatory activities, thereby protecting gastric tissue against indomethacin. These findings highlight the potential of cuminaldehyde as a treatment for gastric ulcers. [ABSTRACT FROM AUTHOR]