Professionalism is a multidimensional concept, defined as conducting oneself with responsibility, integrity, accountability, and excellence. This study aimed to contextualize American Dental Education Association (ADEA) tool on action on professionalism in dental education in Mashhad and apply it in a cross-sectional study.This descriptive-analytic study was conducted on all students of Mashhad School during 2018-2019. The ADEA tool for action on professionalism in dental education was applied. It was firstly contextualized, validated, and its reliability was confirmed by test-retest and Cronbach's alpha. Then, it was applied in a cross-sectional study. Data were analyzed using Lisrel, and SPSS: 16. ANOVA and Tukey's honestly significant difference tests were used to compare the study variables.The tool was valid and reliable for applying in the Iranian context (x2/df <3, RMSEA ≈ 0.1 and indices of comparative fit index, incremental fit index, goodness-of-fit index, and adjusted GFI are >0.7). In the cross-sectional study for measuring professionalism, the mean score of 1st-year dental students was significantly higher than 3rd-year dental students (F = 2.75, P = 0.002). Furthermore, the mean score of 1st-year dental students was also significantly higher than 6th-year students (F = 4.53, P = 0.001). The comparison of the component of professionalism among 1st-to 6th-year students showed that there was no statistically significant difference between the total score of males and females. In addition, no statistically significant difference was found between the total score of local and nonlocal students.The Tool is valid and reliable for applying in the Iranian context. Dental students need to be trained and also practice professional behaviors during their senior years of college.