The present study aimed to evaluate the efficacy of different narrow-leaved lupine seeds (NLL) as a protein source in rabbit diets in terms of growth performance, digestive enzyme activity, nutrient digestion, and nitrogen excretion and retention. The control diet contained 60 g/kg SBM, and the experimental diets, containing 110 g/kg NLL, differed in the varieties used (Boregine, NLLB diet; Jowicz, NLLJ diet; and Rumba, NLLR diet). The proteolytic activity tended to be lower in rabbits fed the SBM diet than in those of the other rabbits. There were higher losses of nitrogen in urine and also a higher total excretion of nitrogen in rabbits fed the NLLJ diet than in rabbits fed the other diets. Consequently, there was a lower nitrogen retention coefficient in these rabbits. There was a higher average daily feed intake in rabbits fed the NLLJ diet than in other rabbits, which led to their worse FCR compared to rabbits fed the other diets. The present study revealed that the varieties of NLL seeds, Boregine and Rumba, represent a suitable dietary CP and can fully replace traditionally used SBM for rabbit diets.