An ameroid constrictor (AC) was placed to occlude the shunt vessel in a dog diagnosed with a single extrahepatic portocaval shunt, and the patient showed favorable outcomes post-surgery. However, the 1-year postoperative assessment revealed that the shunt vessel was completely occluded, but the AC had migrated into the abdominal cavity. The examination of the surgically removed migrated AC revealed an internal space filled with fibrous tissues with no swelling in the casein, and notably, the key remained securely in place. This is the first veterinary medicine case in which migration of the AC without dislodgement of ameroid key was identified.