A phytochemical investigation on the roots of Aconitum austroyunnanense afforded three undescribed aconitine-type C(19)-diterpenoid alkaloids, austroyunnanines A-C (1-3). Structural elucidation of all the compounds were performed by spectral methods such as 1 D and 2 D ((1)H-(1)H COSY, HMQC, and HMBC) NMR spectroscopy. The isolated alkaloids were tested in vivo for their antinociceptive properties. Consequently, austroyunnanine B (2) exhibited significant antinociceptive effect and its ID(50) value (48.0 mumol/kg) was 2-fold less than those of the positive control drugs aspirin and acetaminophen.