Studies on gut microbiome changes in neonatal Korean indigenous calves with diarrhea are rare. In this study, 14 normal calves and 11 calves with diarrhea were selected from Korean indigenous calves up to 30 days of age and classified into three groups at 10-day intervals (1-10, 11-20, and 21-30 days). Feces from 25 calves were collected, and the diversity, similarity, structure, and correlation of the gut microbiome were analyzed.