Eight undescribed β-bergamotene-type sesquiterpene oliganins A-H (1–8) and one known α-bergamotene-type sesquiterpene (9) were isolated from the leaves and twigs of Illicium oligandrum Merr. & Chun. The structures of compounds 1–8 were elucidated by extensive spectroscopic data, and the absolute configurations were determined by using a modified Mosher's method and electronic circular dichroism calculations. The isolates were further evaluated in terms of their anti-inflammatory potential on nitric oxide (NO) generation in lipopolysaccharide-stimulated RAW264.7 and BV2 cells. Compounds 2 and 8 exhibited potent inhibitory effects on the production of NO with IC50 values ranging from 21.65 to 49.28 μM, which were greater than or comparable to those of dexamethasone (positive control). β-Bergamotene-type sesquiterpenes with an α,β-unsaturated ketone exhibited potential nitric oxide inhibitory effect in LPS-stimulated RAW264.7 and BV2 cells with IC50 values ranging from 21.65 to 49.28 μM, which were stronger or comparable than those of dexamethasone. Display omitted •Eight undescribed β-bergamotene-type sesquiterpenes were isolated from Illicium oligandrum.•The stereochemistry of epimeric isomers was determined by ECD calculations.•Two sesquiterpenes with an α, β-unsaturated ketone exhibited potent NO inhibitory activity.