This study aimed to investigate the phagocytic potential of macrophages in progeny of breeder hens kept on an OTA-contaminated diet. For this purpose, 84 White Leghorn (WL) layer breeder hens (40-weeks-of-age) were divided into seven groups (A-G). Hens in Group A were fed a commercial layer ration while those in Groups B-G were kept on a diet amended with 0.1, 0.5, 1.0, 3.0, 5.0, or 10.0 mg OTA/kg, respectively, for up to 3 weeks (n = 12/treatment group; n = 4/time sub-group/treatment group). Fertile eggs were set for hatching on a weekly basis to get the progeny of each week separately. Hatched chicks (n = 10 from each group) were injected with India ink at day 14-of-age to study the in vivo phagocytosis of carbon particles. At day 30, abdominal macrophages were collected from 15 chicks/group and were used to assess their ex vivo/in vitro phagocytic potential against sheep red blood cells (SRBC) as well as for nitrite production upon challenge with lipopolysaccharide (LPS). The phagocytic indices of the reticuloendothelial system of all three sets of progeny (chicks obtained from hens fed OTA for 7, 14, and 21 days) were significantly lower than values seen with Group A chicks. The number of macrophages that were actively phagocytic, the number of SRBC internalized per macrophage, and the extent of nitrite production after stimulation with LPS were each significantly lower in the cells obtained from chicks of breeder hens that had been maintained on the OTA-contaminated diets. The findings of this study clearly showed that there are immunosuppressive effects-in terms of depressed in vivo and in vitro macrophage functionality-in progeny of OTA-fed breeder hens.