Morphological, anatomical, physiological, and nutritional seed characteristics of the lablab bean (Lablab purpureus) were investigated in 46 germplasm accessions, from wild through semi-domesticated forms to landraces and current cultivars. This study aimed to improve the understanding of the domestication process in this tropical crop legume. Wild accessions were distinguished by typical small, brownish and mottled seeds. Cultivated and semi-domesticated forms showed much wider variation in size, colour and shape. Most wild accessions had a thicker seed testa as well as a greater spread of germination over time and larger proportions of hard seeds than most cultivated and semi-domesticated accessions, which germinated more uniformly. Generally, wild accessions showed higher tannin and nitrogen values. In most characteristics, semi-domesticated accessions were intermediate. Not all cultivated accessions combined all typical features of the ‘domestication syndrome’. This was particularly obvious in the dendrogram generated by cluster analysis from a relative domestication index calculated from seed mass and seed-coat texture for any pair of accessions. On the basis of seed characteristics of the germplasm studied, the crop is considered to have originated from Africa.