Background <p>The objective of this study was to investigate the impacts of different dietary soybean meal (SBM) levels on jejunal immunity in nursery pigs at different days post-weaning.</p> Methods <p>Forty-eight pigs (6.2 ± 0.3&#xa0;kg), weaned at 21 days of age, were assigned to 2 dietary treatments (<i>n</i> = 12) in a randomized complete block design and fed for 20 or 42 d in 3 phases (10, 10, and 22 d, respectively). The dietary treatments consisted of low and high SBM diets. On d 20 and 42, jejunal mucosa and tissue samples were collected. Treatments were arranged in 2 × 2 factors with dietary SBM levels (low and high SBM diets) and days post-weaning (20 d and 42 d post-weaning).</p> Results <p>Pigs fed high SBM diets had greater (<i>P</i> &lt; 0.05) relative abundance (RA) of jejunal <i>Prevotella</i>, tended to have greater (<i>P</i> = 0.091) jejunal IgA, had greater (<i>P</i> &lt; 0.05) crypt depth, and tended to have lower (<i>P</i> = 0.064) villus height to crypt depth ratio (VH:CD) than pigs fed low SBM diets. Pigs at 20 d post-weaning had greater (<i>P</i> &lt; 0.05) RA of jejunal <i>Lactobacillus</i> and had greater (<i>P</i> &lt; 0.05) jejunal IL-8 and protein carbonyl than pigs at 42 d post-weaning. Pigs at 20 d post-weaning tended to have greater (<i>P</i> = 0.090) jejunal IgG, tended to have lower (<i>P</i> = 0.059) jejunal IgA, and had greater (<i>P</i> &lt; 0.05) proportion (%) of Ki-67⁺ cells in the jejunal crypt than pigs at 42 d post-weaning.</p> Conclusion <p>Pigs fed high SBM diets showed greater RA of <i>Staphylococcus</i>, a greater immune response, and a decreased VH:CD in the jejunum than pigs fed low SBM diets. Pigs at 20 d post-weaning were more susceptible to jejunal inflammation and intestinal damage than pigs at 42 d post-weaning, but the negative impacts of high SBM diets on jejunal inflammation and intestinal damage were consistent compared to low SBM diets at 20 d and 42 d post-weaning.&#xa0;</p>