The impact of casein diet supplementation with oligosaccharides extracted from lupin and pea seeds on caecal short-chain fatty acids production and nitrogen balance was investigated in Wistar rats. The experimental diets were supplemented with 8% extract from lupin or pea seeds and contained 3.9 or 4.9% of α-galactosides, respectively. The control diet was supplemented with 5% of cellulose. The addition of lupin and pea oligosaccharides increased SCFA production in the caecum, compared to the cellulose control group. The pea extract stimulated acetate and propionate production, whereas the lupin preparation caused the highest caecal butyric acid pool. Amounts of SCFA produced per gram of ingested pea and lupin oligosaccharides were similar. The administration of lupin and pea preparations was accompanied by an increase in ammonia and protein contents in caecal digesta. Feeding oligosaccharides caused higher nitrogen excretion in faeces but had no considerable effect on nitrogen losses in urea nor N retention as compared to the control group.