The aim of this research was to investigate the production traits, blood metabolic profile and fatty acids of meat and tallow in response to the partial replacement of soybean meal with peas in lambs' feed. The research was conducted on 30 Merinolandschaf lambs of 90 days' age over 30 days. Lambs were fed with feed mixture (1000 g day−1 lamb−1). In the control group protein supplement was soybean meal (SC), while in the experimental groups soybean meal was partially replaced with 13 % peas (P13) and 26 % peas (P26). In the haematological parameters of lambs' blood, concentrations of minerals (Ca, P, Mg and Fe) and biochemical parameters (urea, glucose, total protein, albumin, globulins, cholesterol, HDL, LDL, triglyceride, β-hydroxybutyrate and non-esterified fatty acids) as well as enzyme activity (ALT, AST, ALP, GGT and CK) were determined. After slaughter, carcass development was measured. Samples of m. semimembranosus and tallow were taken in which concentrations of fatty acids were analysed. Values of meat pH and colour were taken 45 min 24 h post mortem, and water-holding capacity was calculated. By analysing the production properties of lamb, we found that slaughtering characteristics of lamb carcasses, haematological and most of the biochemical indicators did not differ. Urea concentrations were reduced in the blood of lambs in P13 and P26. Concentration of C18:2 n-6 increased in tallow of lambs of group SC compared to group P26 of lambs. The above-mentioned results indicate the possibility of partial replacement of soybean meal with peas in lambs' diets in organic farming without changes in production.