Calendula officinalis L. (Asteraceae), popularly known as Marigold in Europe and “Calêndula” in Brazil is a medicinal plant used for centuries to treat a wide variety of ailments including gastric ulcers. Despite its folk use, there are few studies about the potential of C. officinalis extract to heal gastric ulcers. In this study, gastric ulcer healing potential of C. officinalis inflorescences (HECO) was evaluated using chronic gastric ulcer induced by acetic acid in Wistar rats. Different groups (n=6) were treated orally with vehicle (water plus 0.5% Tween 80, 1 mL/100 g), omeprazole (20 mg/ kg), or HECO (10, 30 and 100 mg/kg), twice a day for seven days. The results showed that HECO is rich in phenolic substances and displays healing chronic gastric ulcer activity, evidenced by diminished lesion area. Additionally, the data suggest that its effectiveness is related, at least in part, to the capacity of extract to increase production of protective factors of gastric mucosa, such as mucus and antioxidants, and to increase collagen synthesis. This study contributes to the validation of the folk use of the extract of C. officinalis inflorescences for the treatment of gastric ulcer.