Phlogacanthus thyrsiflorus Nees (Acanthaceae) is traditionally used in the North East Himalayan region to treat stomach issues, including gastritis. This study aimed to investigate the gastroprotective effect of 70% aqueous ethanol extract of Phlogacanthus thyrsiflorus flowers (PTE), standardized by HPTLC and LC-MS/MS, and to establish its possible mechanisms. The gastroprotective effect of PTE, at doses of 200 and 400 mg/kg body weight, was evaluated using both physical (pylorus ligation, PL; cold restraint stress, CRS) and chemical (ethanol, EtOH) ulcerogens-induced gastric ulcers in Wistar rats. Animals were randomly divided into control, ulcer control, positive control and PTE-treated groups, with PTE administered orally twice daily for 5 days. The protective effect of PTE was assessed through various gastric ulcer parameters, including gastric pH, gastric wall mucus, non-protein sulfhydryls (NP-SH) content, microvascular permeability, endogenous antioxidant markers, and gastric histopathology. HPTLC and LC-MS/MS confirmed the presence of gallic acid, naringenin, β-sitosterol and ascorbic acid in PTE. The active components of PTE showed significant dose-dependent inhibition of ulcer index, with reductions of 28.59-50.03% in PL, 27.69-53.23% in EtOH and 31.14-57.53% in CRS models (P< 0.01). Additionally, PTE at 400 mg/kg significantly increased gastric pH by 23.41%, mucus content by 33.69%, and NP-SH levels by 37.24%. PTE also demonstrated significant antioxidant potential and histopathological studies confirmed its protective effect. The study suggests that the anti-ulcer effect of PTE may be attributed to its ability to preserve adhered gastric mucus, exhibit antisecretory effects, and scavenge free radicals.