The effects of supplementation of riboflavin along with Bacillus subtilis was investigated on growth performance and intestinal health of broilers under coccidial challenge. Treatments are 3 × 2 × 2 factorial arrangement, which includes 3 levels of riboflavin (0.75, 6.6 (recommended), and 20 ppm), with or without Bacillus subtilis, and with or without coccidial challenge. Coccidial challenge impaired the intestinal morphology and reduced body weight (BW), body weight gain (BWG), and feed intake and increased FCR between d 14-28. However, the cocci impact on birds was reduced along with age, as the effects on internal organs was reduced, which allowed birds to recover. However, coccidiosis reduced overall BW and BWG and increased abdominal fat pad weight and slight woody breast incidence. In conclusion, riboflavin at tested level was unable to enhance growth performance and intestinal health, but its inclusion altered birds response to coccidial challege other than feeding Bacillus subtlis alone.