The optimal timing for endoscopic retrograde cholangiopancreatography (ERCP) in patients with acute cholangitis (AC) remains unclear. The aim of this review is to clarify associations between timing of ERCP and clinical outcomes in patients with AC by discussing the current literature. Briefly, it is shown that ERCP before 72 and 48 hours of hospital admission is associated with reduced incidences of composite adverse outcomes and organ failure, respectively. ERCP before 24 hours seems to be associated with reduced 30-day mortality. Thus, performance of ERCP with biliary decompression within 24 hours from time of hospital admission is recommended in patients with AC.