A total of 30 male piglets (Duroc X Landrace) weaned at the 28th day of age were used to compare the nutrient digestibility of legume seeds and their impact on digestive enzyme activities and morphology of intestinal mucosa sampled at slaughter. Five groups of six piglets were fed a control (C) diet based on casein or a diet in which 50% of crude protein (CP) were supplied by soya bean meal (SBM), pea (P), faba beans (FB), or blue lupin (Lupinus angustifolius) (L), respectively. Total tract (TTAD) and ileal (IAD) apparent digestibilities were measured on the same piglets between the 32nd-39th day and 53rd-60th day of age, respectively. TTAD and IAD of DM, CP and energy were lower in legume-containing diets as compared to the control diet. Among the legume seeds, the lupin-based diet had the lowest TTAD and IAD of DM and energy, but no significant differences were found for the IAD of CP. The height of intestinal villi was the highest with SBM and the lowest with FB only in the duodenum. Crypt depth increased by 50% in the piglets fed the P and FB diets, as compared to controls. Pancreas weight was higher and the duodenal activities of most intestinal enzymes examined were lower with the legume-containing diets.