The aim of the study was to determine the effects of fermentation of Lupinus angustifolius seeds with yeasts and multibacterial preparation on their chemical and microbial composition, protein digestibility and selected gut and lipid blood parameters in rats. Contents of nutrients, fibre fractions, alkaloids, oligosaccharides, amino acids and phytate in raw (RL) and fermented (FL) lupine seeds were determined. The RL and FL seeds and soyabean oil meal were used as the only protein supplements in wheat diets and fed for 4 weeks to 3 groups of 8 male Wistar rats, approximately 7-week-old. Apparent total tract digestibility of protein (ATTD), intestinal tissue and digesta weights, caecal metabolites concentrations and lipid profile in blood were determined. Fermentation did not affect or induced small changes in crude protein, ash, fat, total alkaloids and phytate P concentrations whereas it eliminated oligosaccharides, reduced considerably true protein and increased crude fibre, NDF and ADF contents. The ATTD of dietary protein was higher in rats fed FL than RL diet. Feeding FL vs RL did not affect intestinal tissue weight, decreased caecal and colon digesta weights, decreased pH and activity of α-galactosidase, and increased that of xylosidase in caecal digesta. The short chain fatty acids (SCFA) caecal concentration and profile were not affected by fermentation whereas pools of acetate, butyrate and total SCFA were lowered. Total triacylglycerols blood level did not differ between FL and RL group, nevertheless total cholesterol and HDL concentration were higher in FL fed rats.