Two new anthocyanins (1, 2) were isolated from the stem bark of the castor plant, Ricinus communis L. by a combination of chromatographic techniques. The structures of the compounds were elucidated, mainly by nuclear magnetic resonance spectroscopy and high-resolution electrospray mass spectrometry, to be cyanidin 3-O-β-xylopyranoside-5-O-β-glucopyranoside (1) (21%), and cyanidin 3-O-β-xylopyranoside-5-O-(6′”-O-malonyl-β-glucopyranoside) (2) (79%). In addition, cyanidin 3-O-β-xylopyranoside-5-O-(6′”-O-methylmalonate-β-glucopyranoside) (3), formed by methyl esterification of the malonyl unit of 2 during isolation and storage, was identified.