Aims: The aims of the present study are to characterize the intestinal microbial community displaying a high-adhesive capability in fish, and to evaluate the relationship between mucosal adhesion of intestinal bacteria and fish health and disease. Methods and Results: A total of 707 aerobic bacteria isolated from carp intestine that were maintained under either feeding (feeding group) or no-feeding (no-feeding group) conditions and were performed adhesive assay. Isolates were divided into three categories on the basis of adhesive capability: high-, medium-, and low- adhesive capabilities. The average proportions of isolates with high-adhesive capability in the feeding and no-feeding groups were 30% and 32%, respectively. A phylogenetic analysis using a partial 16S rRNA gene demonstrated that most isolates with high-adhesive capability in both groups were classified as belonging to an Aeromonas group, and populations of isolates within high- and low-adhesive categories were markedly different. Conclusions: Intestinal bacteria with a high-adhesive capability in relation to intestinal mucous always colonize on the surface of intestinal mucosa and grow in the intestinal tract of feeding carp. The adhesive capability of intestinal bacteria is essential for colonization and growth in the intestinal tract of fish. Significance and Impact of the Study: Our results indicate that members of the Aeromonas group with adhesive capability always colonize on the surface of intestinal mucosa.