Acute cholecystitis is not a common complication of gastrectomy. Its clinical presentations and management strategies in old patients have not been well described in available literature. This report describes the clinical features, management strategies, and treatment outcome of acute cholecystitis immediately after gastrectomy. Acute cholecystitis immediately after gastrectomy in old patients has different clinical presentations, such as fever and high plasma C-reaction protein level. Abdominal computed tomography (CT) scan and ultrasonography showed acute cholecystitis in our cases, which was treated with antibiotics and ultrasound-guided percutaneous transhepatic gallbladder drainage (PTGD). The results indicate that abdominal CT scan and ultrasonography can effectively diagnose acute cholecystitis after gastrectomy, which can be effectively treated with antibiotics and PTGD.