Introduction: Interdisciplinary research, which integrates input (e.g., data, techniques, theories) from two or more disciplines, is critical for solving wicked problems. Medical education research is assumed to be interdisciplinary. However, researchers have questioned this assumption. The present study, a conceptual replication, clarifies the nature of medical education interdisciplinarity by analyzing the citations of medical education journal articles. Method: The authors retrieved the cited references of all articles in 22 medical education journals between 2001–2020 from Web of Science (WoS). We then identified the WoS classifications for the journals of each cited reference. Results: We analyzed 31,283 articles referencing 723,683 publications. We identified 493,973 (68.3%) of those cited references in 6,618 journals representing 242 categories, which represents 94% of all WoS categories. Close to half of all citations were categorized as “education, scientific disciplines” and “healthcare sciences and services”. Over the study period, the number of references consistently increased as did the representation of categories to include a diversity of topics such as business, management, and linguistics. Discussion: Our study aligns with previous research, suggesting that medical education research could be described as inwardly focused. However, the observed growth of categories and their increasing diversity over time indicates that medical education displays increasing interdisciplinarity. Now visible, the field can raise awareness of and promote interdisciplinarity, if desired, by seeking and highlighting opportunities for future growth.