Introduction: Self-regulated learning is a cyclical process of forethought, performance, and self-reflection that has been used as an assessment tool in medical education. No prior studies have evaluated SRL processes for answering multiple-choice questions (MCQs) and most evaluated one or two iterations of a non-MCQ task. SRL assessment during MCQs may elucidate reasons why learners are successful or not on these questions that are encountered repeatedly during medical education. Methods: Internal medicine clerkship students at three institutions participated in a SRL microanalytic protocol that targeted strategic planning, metacognitive monitoring, causal attributions, and adaptive inferences across seven MCQs. Responses were transcribed and coded according to previously published methods for microanalytic protocols. Results: Forty-four students participated. In the forethought phase, students commonly endorsed prioritizing relevant features as their diagnostic strategy (n = 20, 45%) but few mentioned higher-order diagnostic reasoning processes such as integrating clinical information (n = 5, 11%) or comparing/contrasting diagnoses (n = 0, 0%). However, in the performance phase, students' metacognitive processes included high frequencies of integration (n = 38, 86%) and comparing/contrasting (n = 24, 55%). In the self-reflection phase, 93% (n = 41) of students faulted their management reasoning and 84% (n = 37) made negative references to their abilities. Less than 10% (n = 4) of students indicated that they would adapt their diagnostic reasoning process for these questions. Discussion: This study describes in detail student self-regulatory processes during MCQs. We found that students engaged in higher-order diagnostic reasoning processes but were not explicit about it and seldom reflected critically on these processes after selecting an incorrect answer. Self-reflections focused almost exclusively on management reasoning and negative references to abilities which may decrease self-efficacy. Encouraging students to identify and evaluate diagnostic reasoning processes and make attributions to controllable factors may improve performance.