Objectives: Substance use disorders have become a major public health problem in Bangladesh. We sought to assess the pattern of substance use and related factors among hospitalized patients. Methods: This was a descriptive study that included 105 patients. All patients who were admitted to a private drug de-addiction clinic in Dhaka, Bangladesh, between 1 July and 31 December 2013 and diagnosed with substance use disorder were enrolled in the study. Data was collected via face-to-face interviews using a semi-structured questionnaire and the information was complemented by the case-notes. Results: Almost all (90.5%) respondents were male and were poly-substance users (91.4%). The mean age of respondents was 28.8±8.0 years. Most (27.6%) respondents used three types of substances. Smoking or inhalation was the route used by most (90.5%) respondents. More than three-fourths (81.0%) of respondents used nicotine. Among the other substances, the majority (79.0%) used opioids, followed by cannabinoids (55.2%), and alcohol (41.0%). Curiosity, peer pressure, and for fun were identified as the common reasons for initiating substance use. Conclusions: A high proportion of poly-substance use was found in the study population. Our findings could help in the management and development of prevention strategies for substance use in Bangladesh.