This study aimed to investigate the safety and efficacy of endoscopic retrograde cholangiopancreatography (ERCP) + EyeMax (single-operator cholangioscopy system; SOC) (i.e., ERCP+SOC) for the treatment of choledocholithasis-associated acute cholecystitis. Twenty-five patients were evaluated between January 2022 and June 2023. The success rate (technical + clinical), procedure time, postoperative recovery, post-operative length of hospital stay, and complications rates were recorded. The procedure and clinical success rates were 92% (23 / 25) and 96% (24/25), respectively. The mean procedure time was 36.6 ± 10 minutes (standard deviation [SD]. The average post-operative hospitalization was 2 ± 0.8 days. No adverse event such as bleeding, perforation, or bile leakage occurred. Colecystitis did not recur during the 2 to 18 months of follow-up. ERCP+SOC may provide a feasible, safe, and effective alternative treatment for acute cholecystitis secondary to choledocholthiasis. ERCP+SOC was able to simultaneously resolved both biliary tract and the gallbladder problems via natural orifice endoscopy. Its advantage included no skin wound, reduced postoperative pain, quick recovery, limited to no exposure to x-rays, and a short hospital stay.