We examined the ethnic origin of authors who published research articles in leading medical journals over the past two decades. We carried out a serial cross-sectional analysis of first and last authors who published original research articles in the British Medical Journal, Lancet, Journal of American Medical Association, and New England Journal of Medicine in 2002, 2012, and 2022. The main outcome was the change in proportion of authors over time according to ethnic origin (Anglo, North/West European, South/West European, Asian, Arab and Middle Eastern, African), gender (male, female), and institutional affiliation in percentage points. Most authors were of Anglo descent (44%), although the proportion of non-European authors grew between 2002 and 2022. East Asian, South Asian, and Arab & Middle Eastern last authors accounted for a greater proportion of authors over time, gaining between 3 to 6 percentage points, while African authors made no gains. Gains were gender-specific, with non-European men gaining 8 points as first and last authors, but non-European women gaining 5 points as last authors only. Most non-European authors were affiliated with North American (42.9%) or European (22.4%) institutions, while non-European authors from other institutions did not make meaningful gains over time. Ethnic diversity of authors in leading medical journals has increased somewhat over time, but non-European men account for most of the gains. Non-European women have yet to make comparable advancement as authors.