Prunella vulgaris L.(Lamiaceae family) species is widespread throughout the world and the fruit-spike is used in folk medicine in many countries. The Romanian resource of Prunellae spica is poorly studied from a phytochemical and pharmacological point of view; accordingly, the present study aimed to evaluate the anti-ulcer action of a hydroalcoholic extract of this species with standardized polyphenol content. The extracts used were phytochemically characterized by the total polyphenol content (TPC) and by the determination of the constituents (phenol-carboxylic acids, flavonoids) by HPLC-MS/MS. Quantitative analysis showed the presence of flavonoids in glycosidic form in fairly large quantities (hyperoside, rutoside, isoquercitrin); on the other hand, smaller quantities of aglycones (quercetol, kaempferol, apigenin) were identified and quantified. Moreover, phenolcarboxylic acids, such as caftaric, ferulic, p-coumaric acid, were measured. Two types of doses (high dose-50 mg/kg body weight (kgbw), respectively low dose 10 mg/kgbw, values expressed in gallic acid equivalents) were administered preventively/curatively in rats with phenylbutazone-induced ulcer; ranitidine at 50 mg/kgbw was used as an activity control. Efficacy was quantified by measuring ulcer index, as well as by examination of gross features and histopathological changes. The hydroalcoholic extracts of Prunella vulgaris L. proved to have a dose-dependent antiulcerous action in curative treatment. As the titratable acidity is not decreased by the treatment, the effect is mediated by the prevention of oxidative inflammation of the mucosa. Histopathological results confirmed these in vivo results. Prunellae spica of Romanian origin is a plant resource rich in polyphenols that has shown protective effects on nonsteroidal anti-inflammatory drugs (NSAID)-related gastric ulcer. The observed effects are dose-dependent, probably mediated by inhibition of oxidative stress in the mucosa and promotion of regeneration processes.