Objectives: Clinical trials are prospective studies on human subjects designed to answer various clinical questions. However, only a limited number of clinical trials have been conducted in Oman. This study aimed to assess the knowledge and attitudes of Omani patients and their relatives towards participating in clinical trials. Methods: This cross-sectional study was conducted between October 2015 and March 2016 among 174 patients and relatives attending the Haematology and Oncology Outpatient Clinics and Day Care Unit of the Sultan Qaboos University Hospital, Muscat, Oman. A self-administered questionnaire was designed to elicit participants' knowledge of and attitudes towards participation in clinical trials. Results: A total of 100 patients and relatives agreed to take part in the study (response rate: 57.5%). The male-to-female ratio was 1:1.2. Only 31.3% of the studied population knew what clinical trials were and only 6.5% had themselves previously participated in a clinical trial. The majority agreed or strongly agreed that they would participate in clinical trials related to their own condition (59.2%). Overall, 89.7% expected to be informed about potential clinical trials by their treating physicians. Conclusion: Omanis had a low level of knowledge of clinical trials and a very low rate of previous participation in such trials, despite a moderate level of interest. Patients should therefore be educated and informed of ongoing clinical trials in order to improve participation rates for clinical trials conducted in Oman. Keywords