The efficacy of narrow-leaved lupine seeds (NLLs) as a dietary crude protein (CP) source compared to soybean meal (SBM) was evaluated in terms of growth performance, nutrient digestion, digestive enzyme activity, nitrogen (N) balance, and N retention in fattening rabbits. The SBM diet contained 60 g/kg SBM, whereas the other diets contained 110 g/kg of different NLL varieties (Boregine, NLLB diet; Jowicz, NLLJ diet; and Rumba, NLLR diet).