ObjectivesTo assess the diagnostic ability in detecting oral lesions among dentists, dental hygienists, dentistry students, oral hygiene students, and non‐healthcare subjects.Materials and MethodsParticipants were invited to classify 30 images of oral lesions in “benign” or “suspected malignant” only based on the visual appearance of the lesion. Diagnostic accuracy was assessed by calculating sensitivity and specificity with 95% confidence intervals and stratified by population group and image features (color, shape, and size of the lesions).ResultsA total of 16,590 examinations by 553 subjects were analyzed. Overall sensitivity and specificity were 57% (95% confidence interval 56%–58%) and 64% (95% confidence interval 63%–65%). Diagnostic accuracy varied among population groups, with experienced dentists showing the lowest sensitivity (52%) and the highest specificity (71%). Red lesions, flat lesions, and large lesions had the lowest sensitivity (42%, 36%, 57%) but the highest specificity (70%, 75%, 76%).ConclusionsWe found worrying low ability to detect suspected malignant oral lesions by both healthcare workers and non‐healthcare subjects. Lesion‐specific characteristics may lead to differences in recognition. Specific courses and more adequate teaching methods should be proposed to increase identification of oral lesions.