The aim of this study was to assess the initial levels of moral reasoning among four cohorts of dental students in the first semester of their first year of study. All 332 students at one U.S. dental school were invited to take the Defining Issues Test 2 (DIT2) during the first semester of their first year while enrolled in a mandatory ethics course in 2015-18. Students’ mean scores on the DIT2 subscales were compared to their gender, underrepresented minority (URM) status, citizenship, English as primary language, and single status. The four subscales were personal interests (PI), in which self-motivated interests are the main focus; maintaining norms (MN), which takes into consideration what is expected from society; post-conventional (PC), which upholds ethical principles that promote the good of society; and N2 index, which indicates one’s ability to discriminate between lower stage and higher stage items. A total of 245 students participated (74% response rate). The results showed no differences between gender, URM status, citizenship, or English as primary language and any of the DIT2 subscales. Single participants scored significantly higher on the PC and N2 subscales and significantly lower on the MN subscale. There was a significant correlation between humanitarian liberalism (HL) and all four subscales. Religious (Christian) orthodoxy (RO) was significantly correlated with MN, PC, and N2. The DIT2 subscale scores were not impacted by various exploratory variables, with the exception of relationship status, which had significantly higher MN and N2 scores. Participants with higher scores on HL and RO had higher moral reasoning scores, and females had higher levels of moral reasoning than males on their PC and N2 scores. These findings have implications for implementing educational activities that may help develop students’ moral reasoning abilities over the course of dental school.