PurposeTolerance for ambiguity (TFA) is important for physicians, with implications for ethical behavior and patient care. This study explores how medical students' TFA changes from matriculation to graduation and how change in empathy and openness to diversity are associated with this change. MethodData for students who took the Matriculating Student Questionnaire (MSQ) in 2013 or 2014 and the Medical School Graduation Questionnaire (GQ) in 2017 or 2018 were drawn from the Association of American Medical Colleges (n = 17,221). Both the MSQ and GQ included a validated TFA scale and a shortened version of the Interpersonal Reactivity Index; the MSQ also included an openness to diversity scale. Tercile groups were used to assess how TFA changed from the MSQ to GQ, and regression analyses were used to assess associations between change in TFA and openness to diversity and between change in TFA and change in empathy. ResultsMean TFA scores decreased (d = −.67) among students with the highest TFA at matriculation but increased (d = .60) among students with the lowest TFA at matriculation. Regression results showed that change in TFA was significantly and positively associated with change in empathy (beta = .05, P < .001) and that openness to diversity (as reported at matriculation) was significantly and positively associated with TFA at graduation (beta = .05, P < .001). ConclusionsThis is the first nationally representative study to suggest that medical students' TFA changes over time, but in different directions depending on TFA at matriculation. TFA over time was also associated with change in empathy and openness to diversity. Medical schools should consider strategies to assess TFA in their admissions processes and for cultivating TFA throughout the learning process.