Background: Only a small proportion of patients with biliary tree infection grow microorganisms in blood cultures. Antibiotics chosen or tailored based on organisms identified on blood cultures have a potential for under-treatment and unfavorable outcomes, including recurrent infection and early stent occlusion. In our current practice, we collect bile for culture if an Endoscopic Retrograde Cholangio-Pancreatography (ERCP) is performed in patients with suspected cholangitis. In this study, we compare the microbial yield of blood cultures and ERCP-obtained bile cultures in patients with ascending cholangitis. Methods: We reviewed medical records of all the patients treated for ascending cholangitis who had blood cultures and ERCP-obtained bile cultures at a tertiary care center between 2010 and 2016. Bile was collected for culture before injecting contrast, via a catheter after discarding the initial 3 mL. Results: Ninety-three patients were included with mean age of 71 (±15) years. Out of 93 patients, 11 (12%) had prior sphincterotomy, 29 (31%) had an indwelling biliary stent, and malignant obstruction was the most common etiology (34%). ERCP-obtained bile cultures were positive in 90 out of 93 (97%) patients with monomicrobial growth in 34 out of 93 (39%) patients. Mixed intestinal flora was noted in 3 patients. Blood cultures were positive in only 30 out of 93 patients (32%) and 24 out of 93 (26%) patients had monomicrobial growth. Totally 26 out of 30 patients (87%) grew the same organism as the bile culture, 3 grew an organism different from bile cultures, and one had no growth in the bile culture. On multivariable analysis, the presence of an indwelling biliary stent was the lone factor associated with polymicrobial growth, 83 vs. 52%, p = 0.007. Conclusion: ERCP-obtained bile cultures are a reliable and feasible mechanism to evaluate patients with suspected biliary tree infection. This technique has a significantly higher yield when compared to blood culture. Selection and tailoring of antibiotics based on bile culture in the management of ascending cholangitis are advised.