Pseudoaneurysm of the cystic artery is very rare. It usually presents with rupture and hemorrhagic shock, which may be life-threatening. Ultrasonography and contrast-enhanced tomography can be used for the diagnosis. The mainstay of treatment for this disease is cholecystectomy. Here we present an 86-year-old man with known diabetes and Alzheimer's disease whose pseudoaneurysm was treated with percutaneous thrombin injection and highlight the technical aspect of the procedure. With ultrasonography guidance, a 21-gauge Chiba needle was passed through the liver and advanced into the pseudoaneurysm sac. A controlled, slow injection of 0.5-cc thrombin into the sac was performed with instant occlusion. Doppler imaging performed immediately following the procedure revealed that the pseudoaneurysm was not filled. Pseudoaneurysm of the gallbladder is extremely rare, and its diagnosis is difficult. If the condition is not treated right away, it can quickly become life-threatening. The majority of the pseudoaneurysms have already ruptured, and the patients are clinically septic, making surgery dangerous. Also, the use of contrast media in these patients may increase the risk of nephropathy, which is not an issue with percutaneous injection. Due to the obvious risk of rupture and bleeding, we propose injecting pseudoaneurysms only if they have a visible wall. Percutaneous injection of the gallbladder pseudoaneurysms can be an option when treating gallbladder pseudoaneurysms. More research on long-term success rates is required.