Background: Environment is important component of communication skills. Physicians’ communication style including attire may influence patient perceptions. Previous studies mostly based on pictures of providers in different attires provide conflicting evidence. This RCT aimed to explore the effects of physician attire on patients’ perceptions of compassion, professionalism and physician preference. Hypothesis was that patients will perceive the doctor in formal attire as more compassionate than the doctor wearing casual attire. Methods: 105 English speaking adult follow-ups at outpatient supportive care center, were randomized to watch 2 standardized, 3-minute video vignettes, with similar script, depicting a routine clinic encounter. In one video, physician was wearing formal attire with tie and buttoned up white coat, while in the other, physician was in casual attire without a tie or white coat. Actors and patients were all blinded to purpose of the study. Investigators were blinded to the videos watched by patients. After viewing each video, patients completed validated questionnaires rating their perception of physician compassion (0 = best, 50 = worst) and professionalism (5 = poor, 25 = very good). Patients were also asked to rate their preference for the physician. Results: There were no significant differences between formal and casual attire for compassion [median (IQR), 25 (10, 31) vs 20 (8, 27); P = 0.31] and professionalism, [17 (13, 21) vs 18 (14, 22); P = 0.42]. 32 (30%) patients preferred formal, 33 (31%) preferred casual attire and 40 (38 %) patients had no preference. Subgroup analysis did not show significant differences among age, sex, marital status and education level for compassion, professionalism and physician preference. Conclusions: Doctor’s attire did not have an effect on patients’ perception of physicians’ level of compassion and professionalism. Dress code also did not influence the patients’ preference for their doctor or their trust and confidence in the doctor’s ability to provide care. There is need for more RCTs in area of communication skills specifically to better understand the impact of different attires on patient perceptions. Clinical trial information: NCT03168763