A new iridoid, named nudifloside (1), together with three known compounds, was isolated from the EtOH extract of the aerial parts of Callicarpa nudiflora Hook. The structures were elucidated by a study of their physical and spectral data. Nudifloside (1) and the isolated known compound linearoside (2) displayed inhibitory effects towards chronic myelogenous leukaemia K562 cell line, with IC(50) values of 20.7 and 36.0 microg mL(-1), respectively.