This study aimed to investigate the effect of citric (CA) and fumaric (FA) acids (0, 15 and 30 g/kg diet for each) on nutrients digestibility, the population of bacteria inhabiting the gut, histopathological changes in the intestine and lymphoid organs and meat physical characteristics of broilers. One–hundred twenty-one-day old unsexed "Cobb" chicks were randomly distributed into five treatments of three replicates eight chicks each. Control (no additives), 15 g CA, 30 g CA, 15 g FA and 30 g FA were evaluated from 0 to 6 weeks of age. Dry matter, crude protein (CP), ash, calcium (Ca), and phosphorus (P) apparent digestibility were significantly improved by 30 g FA/kg diet compared to the control. Fumaric acid at 30 g/kg diet showed higher ether extract, and nitrogen free extract apparent digestibility compared to the control. A significant increment in P and a non-significant higher CP, ash, and Ca apparent digestibility were noticed in 30 g CA/kg diet compared to the control. A significant reduction in total bacterial and total Enterobacteriaceae counts in all acid treatments compared to the control, with the least count in 30 g FA/kg diet group. The ileum of organic acids treated birds expressed a healthy intestinal structure with an abundance of goblet cell proliferation. Lymphoid organs showed mild to moderate hyperplasia of their lymphoid follicles indicating immune response improvements. It could be concluded that acids supplementation improved gut microbiota, immune response and apparent nutrients digestibility.