The objective of this study was to determine the prevalence and factors associated with multidrug-resistant tuberculosis (MDR-TB) at Siriraj Hospital, Bangkok, Thailand. We conducted a retrospective unmatched case-control study of patients clinically diagnosed and microbiologically confirmed to have tuber- culosis (TB) at Siriraj Hospital from 2010 to 2012. Patient characteristics, clinical data, microbiological findings, outcomes and drug susceptibilities were recorded. A total of 188 subjects were included in the study; 52.1% (98) were males; the mean age was 48.9 years. Subjects were categorized into one of two groups, as follows: non-MDR-TB (141 patients) and MDR-TB (47 patients). The prevalence of MDR- TB was 2.6%. Co-morbidities of study subjects included diabetes mellitus (16.5%), HIV infection (16%) and cancer (5.9%). One hundred thirty-one patients (69.7%) had pulmonary TB. Factors significantly associated with MDR-TB were age < 65 years (OR = 6.94; 95% CI: 1.02-45.49; p = 0.048), history of TB (OR = 51.86; 95% CI: 12.35-217.79; p < 0.001), HIV co-infection (OR = 3.83; 95% CI: 1.02-14.38; p = 0.047) and alcohol consumption (OR = 3.90; 95% CI: 1.03-14.72; p = 0.045). Of the 146 patients for whom a clinical outcome was available, 51 (34.9%) had an unfavorable outcome. Poor compliance (OR = 13.51; 95% CI: 3.97-45.45; p < 0.001) and previous history of TB (OR = 8.16; 95% CI: 1.76-37.73; p = 0.007) were associated with an unfavorable outcome. MDR-TB was significantly associated with: patients aged < 65 years, those with a previous history of TB, those with HIV co-infection and those who drank alcohol. These factors should be kept in mind when treating TB patients at Siriraj Hospital, Thailand.