Background: Malignant biliary obstruction (MBO) is a common complication in cases of locally or systemically advanced gastrointestinal malignancies. Placing a biliary stent is a method to relieve blockages in the biliary tract with fewer chances of bacteriobilia after endoscopic retrograde cholangiopancreatography (ERCP). Materials and methods: This retrospective study was carried out in the Department of Microbiology at a teaching hospital. The hospital information system and the case files for the ward data entry were used to collect the clinical data of every patient. Records of management using biliary drains were also analyzed. SPSS 20.0 was used for all analyses (SPSS Inc., Newark, NJ). Results: This study included 95 cancer patients undergoing ERCP. The most common tumor we encountered was advanced carcinoma gallbladder (42/95, 44.21%) and the average age of patients was 51.63 +/- 12.68 years. Eighty-one bacterial isolates were isolated from the 62 patients who developed bacteriobilia. Escherichia coli (29/81, 35.80%) was the most common microorganisms isolated. The 48 multidrug-resistant (MDR) microorganisms were isolated. Female gender (p = 0.037), presence of cholecystitis (p = 0.019), and increased length of hospital stay (p = 0.032) were considered important risk factors linked to the isolation of MDR bacteria from cancer patients undergoing ERCP. Patients with increased levels of procalcitonin >=0.5 ng/mL (normal range, 0-0.4 ng/mL) and had a considerably worse 60 days survival in comparison to cancer patients with procalcitonin levels <0.5 ng/mL. Conclusion: This study suggested increased chances of bacteriobilia and MDR due to prolonged placement of the biliary stenting following ERCP.