ABSTRACT The capacity of the chicken intestinal tract to digest and absorb nutrients is not fully developed on the day of hatch. The aim of this study was to investigate the role of betaine on the intestinal development of broiler chickens, including brush border enzyme activities indices and morphological changes during the first week of growth. Fiftyone-day-old Ross 308 broiler chickens were randomly distributed into five groups: control (C), low methionine(LM), low methionine plus betaine (LM+B), betaine 1 (B1) and betaine 2 (B2). Betaine was dissolved with a concentration of 500 mg/L in the drinking water of LM+B and B1groups and a concentration of 1000 mg/L in the B2 group. Histological assessment showed lower duodenal crypt depth and villi height/crypt depth ratio in B1 as compared to C. Jejunal villi height of B2birds was significantly higher than that of C birds, whereas jejunal crypt depth values of both B2 and LM birds were higher relative to LM+B and C birds. Betaine-fed groups had significantly a thicker ileal muscularis mucosa layer than C and LM groups. Duodenal and jejunal g-glutamyl transferase activity was significantly higher in B2birds in LM birds. Alkaline phosphatase activity in all three segments of the small intestine was significantly higher in the LM birds than in other groups. Jejunal alanine aminopeptidase activity in LM birds was significantly higher than in other groups, particularly in B1 and B2. The results suggest that betaine may be a promising agent to promote the intestinal development of broilers fed low-methionine or standard diets.