Two new isopimarane diterpenes, 1α‐hydroxy‐14α‐methoxyisopimara‐8(9),15‐diene (7) and 1α,14α‐dihydroxyisopimara‐8(9),15‐diene (9) and eight known isopimarane diterpenes including (‐)‐sandaracopimaradiene (1), 6β‐acetoxysandaracopimaradiene‐9α‐ol (2), sandaracopimaradiene‐7β,9α‐diol (3), sandaracopimaradiene‐1α,9α‐diol (4), 6β‐acetoxysandaracopimaradiene‐9α‐ol‐1‐one (5), 6β‐acetoxysandaracopimaradiene‐1α,9α‐diol (6), 6β,14α‐dihydroxyisopimara‐8(9),15‐diene (8), and 6β,14β‐dihydroxyisopimara‐8(9),15‐diene (10) were isolated from hexane fraction of Kaempferia galanga ethanol extract. Compounds 5, 6, 8, and 9 exerted the good anti‐inflammatory effect on lipopolysaccharide‐stimulated nitric oxide production from RAW264.7 cells with IC50 of 11.2, 7.7, 14.3, and 12.1 μM, respectively. These four compounds inhibited nitric oxide synthase (iNOS) mRNA expression. Compounds 5 and 6 also suppressed cyclooxygenase 2 (COX‐2) mRNA expression; in addition, compound 6 had mild inhibitory effect on TNF‐α mRNA. Among these compounds, 5 dramatically inhibited iNOS and COX‐2 mRNA expression. The influential structures were proposed to be oxygen substitute at C‐1, C‐6, and α‐OH at C‐14.