The relationship between the cardiac glycoside contents in Corchorus olitorius seeds and the seed color was examined. The seed color was assigned a shade (color value) (L value in UCS system). The dark grayish green seeds, showing lower L value, contained more cardiac glycosides than dark grayish yellow seeds showing higher L value. When the total cardiac glycoside contents were plotted against the L values, a positive correlation (r = ‐0.913) was observed. Also, there was a higher content ratio of strophanthidin glycosides (erysimoside and olitoriside) in the seeds showing lower L value, while there was a lower content ratio of digitoxigenin glycosides (coroloside and glucoevatromonoside) in the seeds showing lower L value.