Aims: To characterize the antimicrobial and adhesion ability of candidate probiotic Clostridium butyricum CB2 for farmed fish in vitro. Methods and Results: The potential probiotic Cl. butyricum CB2 had been evaluated for its adhesion capacity and antagonistic effect against two fish pathogens Aeromonas hydrophila and Vibrio anguillarum by the intestinal cell model. In addition, the aggregation ability and antimicrobial property on agar plate were assayed. The results indicated that the candidate probiotic Cl. butyricum CB2 have strong adhesion property and a higher antagonistic activity to Aer. hydrophila and V. anguillarum both on agar plate and cell model. Clostridium butyricum showed a higher aggregation which might be the reasons for bacteria adhesion and antimicrobial activity. Conclusions: The strain Cl. butyricum CB2 could be used as potential probiotic to inhibit pathogens growth and prevent their colonization in fish intestinal tract. Significance and Impact of the Study: This study revealed the antimicrobial and adhesion characteristic of Cl. butyricum CB2 which was selected as the potential probiotic to farmed fish.