The aim of the study was to examine the possibility of substituting infrared-irradiated pea seeds for soybean meal as a protein source in mixtures for broiler chicks, and to determine the impact of such substitution on selected indicators of the performance and health status of the birds. The study was conducted on 150 308 Ross chickens divided into three groups: control (K), group I, and group II. The mixture for the control group was based on cereals and soybean meal (SBM), whereas in groups I and II, 50% and 100% of SBM protein, respectively, were replaced with protein from infrared-irradiated pea seeds. Bird performance was measured in body weight gains and feed consumption, and EWW was calculated. Nutrient digestibility coefficients were also calculated, and slaughter analyses were performed. In blood samples, hematological and biochemical indicators were estimated to evaluate the health of the birds. The complete replacement of soybean meal with pea seeds resulted in a decrease (P < 0.05) of average daily gains of chickens in group II of up to 17%. Production performance in group I after a partial (50%) replacement of SBM with pea seeds was similar to that in the control group. The digestibility of basic nutrients in the final period of fattening was similar in all groups. The replacement of soybean meal with peas did not affect slaughter performance or the proportion of breast muscles and leg muscles in the carcass. Compared with the control group, in both experimental groups a decrease was noted (P < 0.05) in the Ht value (by 23% and 19% in groups I and II, respectively), and in group I a lower (P < 0.05) RBC count (by 16%) was observed. A decreased count of WBC (P < 0.05) (by 14% and 24% in groups I and II, respectively) and a reduced total cholesterol level (by about 15% in both experimental groups) were observed as well. In the blood of birds from group II, the total protein was reduced (P < 0.05) by approximately 9% and uric acid by 19% in comparison with the control. The AST activity in group I was lower (P < 0.05) than in the control. In both groups receiving irradiated peas in mixtures, urea in blood was reduced (P < 0.05) compared with the control birds (by approximately 14% and 12% for groups I and II, respectively). No differences in ALP, ALT and LDH activities were noted among the groups. The results confirm the usefulness of substituting irradiated pea seeds for 50% of soybean meal protein in mixtures for broiler chicken.