This experiment was conducted using 192 day-old Ross 308 chicks, divided into 4 groups of 4 replicate consisting 48 birds. Group I was fed a control diet, Group II was fed control diet supplemented with 0.5 ppm T-2 toxin for 5 weeks, Group III was fed control diet supplemented with 8 × 108 cfu/mL of Mycoplasma gallisepticum, and group IV was fed control diet supplemented by T-2 toxin and Mycoplasma gallisepticum. Body weight and feed conversation ratio (FCR), relative organ weights, clinical signs, biochemical characteristics, and gross and histopathological lesions were recorded in the experimental groups at the end of the second and fifth weeks of age. Body weight and relative weights of bursa of Fabricius, thymus, and spleen decreased and FCR increased significantly (P ≤ 0.05), but the relative weights of liver and kidney showed no significant decrease (P ≤ 0.05) in the serum total proteins, albumin, and increase in aspartate aminotransferase and alanine transaminase were observed in T-2 toxin and T- 2 accompanied with Mycoplasma fed birds when compared to the control group. Liver was enlarged, friable, and yellowish discoloration with distended gall bladder was noticed. Lymphoid organs such as bursa of Fabricius, thymus, and spleen were atrophied in group II and group IV throughout the study. Microscopically, liver showed vacuolar degeneration of hepatocytes, with increased Kupffer cell activity, bile duct epithelial hyperplasia, and infiltration of inflammatory cells. Kidney showed vacuolar degeneration of tubular epithelium along with pyknotic nuclei. Lymphoid organs showed lymphocytolysis and depletion with prominent reticuloepithelial cells. Proventriculus revealed desquamation of villous epithelial cells and lymphoid infiltration in submucosa. Heart showed mild hemorrhage with infiltration of inflammatory cells. Lung showed edema and inflammatory cells in the bronchioles. Trachea showed desquamation and erosions of mucosa. Proliferation of mucosal glands wi
