Several broiler flocks in Behira governorate, suffered from growth retardation that caused a lot of economic losses. Thus, this study was done to identify some of the probable causes and their pathological picture. Samples were collected from 50 broiler chicken flocks, suffering from retarded growth during 2018–2021. Chicken anemia virus (CAV) was detected by PCR in five flocks (10%), meanwhile avian reovirus (ARV) was detected by RT-PCR in 29 flocks (58%). Antibodies of ARV and CAV were detected by ELISA in 86% and 12% from the examined flocks, respectively. Five serotypes of E. coli (O86a, O112, O128, O114, and O55) were isolated from 19 flocks (38%). C. perfringens was isolated from 26 flocks (52%). The observed pathological features were associated with hyper activity of intestinal mucus secreting cells, elongation of cryptal intestinal villi which were partly filled with inflammatory cells and depletion of Payer's patches of ileum. Pancreas showed degeneration and vacuolation of acinar cells. Proventriculus showed dilation of glandular acini, necrosis and sloughing of the glandular epithelium. Bursa showed lymphocytic depletion and atrophy of the bursal follicle, these changes were associated with lymphocytic depletion within the spleen and thymus. Additionally, apoptotic bodies were detected in liver and thymus. This study can indicate the presence of several causes to growth retardation (in vivo) that can do a synergistic effect to aggravate the problem.