Introduction Inappropriate use of abbreviations and acronyms in healthcare has become an international patient safety issue. The aim of this study was to assess the knowledge of medical abbreviations and acronyms among residents of the department of medicine at a tertiary-care hospital. Methods Internal medicine residents (IMRs), subspecialty residents (SRs) and students were asked to complete a self-administered questionnaire which comprised standard abbreviations used in medicine and its various subspecialties. Scores obtained by the residents were classified into three categories: >70% correct answers; 50-69% correct answers; <50% correct answers. Results A total of 77 IMRs, SRs and medical students participated. Overall, good responses were achieved by 53 (68.8%), 16 (20.8%) attained satisfactory responses, and eight (10.4%) had unsatisfactory scores. The majority of SRs achieved good responses (19/22 (86%)), followed by IMRs (30/40 (75%)) and students (4/15 (26.7%)). Evaluation of their knowledge taken from the list of ‘do not use’ abbreviations showed that 89.6% reported using ‘Q.D.' instead of ‘once a day’, and 93% used ‘IU’ instead of the entire phrase ‘international unit’. The top five ŉot to use’ abbreviations were ZnSO4, mg, MgSO4, IU and SC, with the frequency 100%, 96%, 94.8%, 93% and 90%, respectively. Conclusions This study showed that there is a knowledge gap among trainees in medicine regarding the meaning and usage of common medical abbreviations. We therefore recommend proper education of trainees in medicine to ensure they understand the meaning of abbreviations and are aware of the list of ‘do not use’ abbreviations.