INTRODUCTION: Sepsis is always a serious, life-threatening condition, with high mortality rate varying from 30-50% (40-70% in septic shock) in the developed countries, and in developing countries as well. Antibiotic resistance is an important factor in sepsis management. GOAL: To evaluate the resistance patterns of microorganisms, to analyze the correlation between outcome of sepsis patient and multidrug resistant bacterial infection. MATERIALS AND METHODS: This study was designed as a prospective observational study and conducted in a nine bed multidisciplinary intensive care unit (ICU) of a tertiary teaching hospital in Ulaanbaatar, during January 2011 - August 2012. The ICU treatment outcome and length of stay were compared between the patient groups which infected by resistant and non-resistant bacteria. RESULTS: The positive rate of extensively resistant (XDR) and multi drug resistant bacteria by culture test were 22% and 25.1%, respectively. Fifty one percent of sepsis patients were infected by one or more resistant bacteria. Bacteria with an exceptionally high rate of antibiotic resistance (≥60%) were Acinetobacter baumannii, Enterobacter spp and coagulase-negative Staphylococci. Sepsis patients who were infected with resistant bacteria received more mechanical ventilation, renal replacement therapy and suffered from multiple organ dysfunctions when compared to sepsis patients with nonresistant bacterial infection. The length of stay in the ICU was longer in sepsis patients with resistant bacteria but the mortality rate in the ICU did not significantly differ between groups. However, a higher fatality rate was noted in sepsis patients infected with resistant bacteria. In conclusion, resistant bacteria were detected in up to 50% of microbiological samples from critically ill sepsis patients in the ICU of a tertiary teaching hospital in Ulaanbaatar. Antibiotic resistance appears to be a relevant problem of sepsis management in a Mongolian ICU setting.