Modification of the mucosa‐associated intestinal immune system of female C57BL/6 mice was studied during consumption of the Lieber‐DeCarli diet supplemented with 5% v/v ethanol or laboratory chow with ethanol (20% w/v) in the drinking water. All groups received ethanol for 11 weeks. Mice fed the Lieber‐DeCarli diet had fewer CD8+ cells/villus than the chow‐fed controls. Mice that received ethanol in the drinking water had fewer IgA‐containing cells and CDB+ cells than controls. There were no differences in the number of cells in the mesenteric lymph nodes between ethanol‐treated mice and their respective controls. Nevertheless, chow‐fed control mice had more cells than those fed the Lieber‐DeCarli control diet. Although no differences were detected in the percentages of CD4+, CD8+, LECAM‐1+, and LECAM‐1+ CD4+ cells, there was a decrease in the percentage of LECAM‐1+ CD8+ cells in ethanol‐fed mice when compared with their Lieber‐DeCarli controls. Mice receiving ethanol in the drinking water showed alterations in the CD4 CD45RC subsets and in the CD8 CD45RC subsets. Similar results were observed in mice receiving Lieber‐DeCarli diets alone or supplemented with ethanol. The low dose, chronic exposure of dietary ethanol in the Lieber‐DeCarli‐fed mice did not significantly affect the numbers of various thymocyte subsets. But, a decrease in the percentage of CD4‐ CD8+ cells was observed in the thymus of mice receiving ethanol in the drinking water. Chronic ethanol consumption caused significant decreases in the number of CD8+ and IgA+ cells in the intestinal lamina propria, important in mucosal immune defenses.