Objectives The chemical study of a dichloromethane extract from Azorella compacta was directed to the isolation of characteristic mulinane and azorellane diterpenoids in order to determine their gastroprotective activity. Methods Usual chromatographic techniques on the extract led to the isolation of 12 compounds, which were identified by their spectroscopic properties. The HCl/ethanol-induced gastric lesions model in mice was used to determine the gastroprotective activity. Key findings The new diterpenoids, 13β-hydroxymulinane (1), mulin-11,13-dien-20-ol (2), 13α- methoxyazorellanol (3) and mulin-11,13-dien-18-acetoxy-16,20-dioic acid (12) were isolated from A. compacta. The known diterpenoids mulin-11,13-dien-20-oic acid (4), 13α-hydroxyazorellane (5), 13β-hydroxyazorellane (6), mulinic acid (7), mulinolic acid (8) and azorellanol (9), and the aromatic compounds 5,7-dihydroxychromone (10) and isoflavonoid biochanin A (11), were also obtained from the extract. Compounds 6, 9 and 12 at 20 mg/kg reduced gastric lesions by 69%, 71% and 73%, respectively, being statistically similar to lansoprazole at the same dose. Conclusions The results corroborate the intraspecific chemical variations detected previously in specimens of A. compacta collected at different Chilean latitudes. A high concentration of azorellanol (9) could account in part for some of the therapeutic properties attributed to this species, in particular in ulcer treatment. Most of the mulinane and azorellane diterpenoids isolated in this study showed relevant gastroprotective activity at a low dose in the bioassay. © 2013 Royal Pharmaceutical Society.