The use of feed additives containing glutamine can influence the growth and development of piglets during the weaning period. The aim of this study was to determine the effect of feed supplementation with 0.5% L-glutamine on selected parameters of the nonspecific immune response of pigs. The research was carried out on 60 pigs (Polish Large White × Polish Landrace), from 28 days of age to slaughter. The obtained results showed an increased percentage of phagocytic cells (monocytes and granulocytes) and oxygen blast cells in pigs between 28 and 70 days of age, proving that non-specific immune mechanisms were stimulated, which contributed to the improvement of the processes of antigen elimination from the body. The increase in the percentage of cells expressing SWC3, CD11b/CD18+, CD14+ and CD14+CD16+ molecules on granulocytes and monocytes during this period resulted in the enhancement of the host defense mechanisms by stimulating phagocytosis and enhancing the mechanisms of a non-specific immune response. The high concentration of TNF-α and IL-1β as well as Il-10 in the experimental group indicates the cellular phenotype of the Th1-type response, and the maintenance of the immune balance between the pro-inflammatory and anti-inflammatory responses and ensuring the homeostasis of the organism.