The paper investigates seed coat characteristics (as a percentage of overall seed diameter) in Lupinus angustifolius L., a potential forage crop. In the study ten L. angustifolius genotypes, including three Polish cultivars, two Australian cultivars, three mutants originated from cv. 'Emir', and one Belarusian and one Australian breeding line were evaluated. The highest seed coat percentage was recorded in cultivars 'Sonet' and 'Emir'. The lowest seed coat thickness percentage (below 20%) was noted for breeding lines 11257-19, LAG24 and cultivar 'Zeus' (17.87%, 18.91% 19.60%, respectively). Despite having low seed weight, the Australian line no. 11257-19 was characterized by a desirable proportion of seed coat to the weight of seeds. In general, estimation of the correlation coefficient indicated a tendency that larger seeds had thinner coats. Scanning Electron Microscopy images showed low variation of seed coat sculpture and the top of seeds covered with a cuticle. Most of the studied genotypes were characterized by a cristatepapillate seed coat surface, formed by elongated polygonal cells. Only breeding line no. 11267-19 had a different shape of the cells building the surface layer of the coat. In order to illustrate genetic diversity among the genotypes tested, 24 ISSR primers were used. They generated a total of 161 polymorphic amplification products in 10 evaluated narrow-leaved lupin genotypes. © 2014 Clements et al.