Introduction: Multiple studies since the ‘90’s demonstrate that ED staff fail to identify delirium in up to 75% of older patients. Those patients who are discharged have a 3-fold increased mortality. Methods: We iteratively developed a 14-item interprofessional tool with 4 clinical vignettes to assess comfort, knowledge and ability to identify delirium among medical students, EM residents, staff MDs and RNs. We conducted a prospective observational study using modified Dillman survey methodology. Surveys were sent on paper to residents and nurses and online to medical students and staff MDs. Results: Our response rate was 68% (38/56) for residents, 80%(16/20) for RNs; but only 37%(13/35) for staff MDs and 13%(139/1036) for medical students. Comfort with identifying delirium increased with level of medical training; 38/139(27%) 1st-4th year medical students (MS1-MS4); 25/38(66%) 1st-5th year residents (R1-R5); and 12/13(92%) staff physicians reported being comfortable (χ2=34.7, df=2, p<0.001). MS1-MS2 were the least comfortable, with only 5/82(6%) reporting comfort, increasing to 33/57(58%) among MS3-MS4 (χ2=44.9, df=1, p<0.001). A greater proportion of R4-R5 who completed a geriatric emergency medicine (Geri-EM) curriculum reported comfort, 11/12(92%) compared to 14/26(54%) of R1-R3 (χ2=19.2, df=1, p<0.05). Only 5/16(31%) nurses reported being comfortable with identifying delirium. Ability to identify all 4 clinical vignettes correctly was higher among MS3-MS4 than MS1-MS2 (32/57(56%) vs. 30/82(37%), χ2=5.2, df=1, p<0.05). There was no difference between respondents from different levels of medical training (62/139(45%) MS1-MS4, 21/38(55%) R1-R5 and 6/13(46%) staff MDs, χ2=1.4, df=2 p=0.52). There was no effect of Geri-EM completion on perfect vignette scores (6/12(50%) R4-R5 vs. 15/26(58%) R1-R3, χ2=0.20, df=1, p=0.66). There was a trend towards a lower proportion of nurses who identified all 4 clinical vignettes correctly compared to physicians (4/16(25%) vs. 27/51(53%), χ2=3.82, df=1, p=0.051). Conclusion: Our tool may be useful for assessing comfort and knowledge of delirium among ED physicians and nurses. Completion of the Geri-EM curriculum was associated with increased comfort with detecting delirium but not knowledge. Future studies should assess current ED delirium comfort and knowledge at different levels of training; between professions and examine differences nationwide.