Protected sodium butyrate (PSB) is considered an alternative to antibiotics in broiler diets. The present study investigated the effect of PSB supplementation on growth performance, carcass traits, relative weight of internal organs and intestinal morphology in broilers. A total of 1200 one-day-old New Lohman male broilers were randomly allocated to two dietary treatment groups (6 replicates, 100 birds per treatment) and fed a basal diet (CON) or a diet supplemented with 1 g of PSB per kg of diet for 5 weeks of the rearing period. On days 21 and 35, one bird per replicate was randomly selected and slaughtered to determine carcass traits, relative weight of internal organs, and measurements of intestinal histomorphological parameters. The results showed that dietary treatment with PSB increased body weight and average daily gain, but it also led to increased mortality rate (P < 0.05) on day 35 compared to the control group. Furthermore, PSB supplementation increased liver weight, jejunum length and colon length, while decreasing heart weight (P < 0.05) on day 21. In the PSB group, there was a decrease in the number of crypts in the jejunum and an increase in the height of the villi in the ileum (P < 0.05). In conclusion, on day 21, PSB supplementation resulted in an increase in broiler digestive organ parameters, especially liver weight and intestinal morphology. Furthermore, improved growth performance of broilers was recorded on day 35.