Phytochemical investigation on the roots of Aconitum pseudostapfianum resulted in the isolation of three new aconitine–type C19–diterpenoid alkaloids, pseudostapines A–C (1–3). Their structures were determined by spectral methods such as 1D and 2D (1H- 1H COSY, HMQC, NOESY and HMBC) NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated alkaloids were tested in vivo for their antinociceptive potential. As a result, pseudostapine C (3) showed 2-fold more potent antinociceptive effect (ID50 = 60.3 μmol/kg) than the positive control drugs aspirin and acetaminophen. © 2021 Informa UK Limited, trading as Taylor & Francis Group.