Abstract Background The 2023 Duke–International Society of Cardiovascular Infectious Diseases (ISCVID) criteria for infective endocarditis (IE) were introduced to improve classification of IE for research and clinical purposes. External validation studies are required. Methods We studied consecutive patients with suspected IE referred to the IE team of Amsterdam University Medical Center (from October 2016 to March 2021). An international expert panel independently reviewed case summaries and assigned a final diagnosis of “IE” or “not IE,” which served as the reference standard, to which the “definite” Duke-ISCVID classifications were compared. We also evaluated accuracy when excluding cardiac surgical and pathologic data (“clinical” criteria). Finally, we compared the 2023 Duke-ISCVID with the 2000 modified Duke criteria and the 2015 and 2023 European Society of Cardiology (ESC) criteria. Results A total of 595 consecutive patients with suspected IE were included: 399 (67%) were adjudicated as having IE; 111 (19%) had prosthetic valve IE, and 48 (8%) had a cardiac implantable electronic device IE. The 2023 Duke-ISCVID criteria were more sensitive than either the modified Duke or 2015 ESC criteria (84.2% vs 74.9% and 80%, respectively; P < .001) without significant loss of specificity. The 2023 Duke-ISCVID criteria were similarly sensitive but more specific than the 2023 ESC criteria (94% vs 82%; P < .001). The same pattern was seen for the clinical criteria (excluding surgical/pathologic results). New modifications in the 2023 Duke-ISCVID criteria related to “major microbiological” and “imaging” criteria had the most impact. Conclusions The 2023 Duke-ISCVID criteria represent a significant advance in the diagnostic classification of patients with suspected IE. In a cohort of 595 patients with suspected infective endocarditis (IE), the 2023 Duke-ISCVID criteria had better sensitivity than the 2000 modified Duke and 2015 European Society of Cardiology (ESC) criteria for IE and better specificity than the 2023 ESC criteria. Graphical Abstract Graphical Abstract This graphical abstract is also available at Tidbit: https://tidbitapp.io/tidbits/external-validation-of-the-2023-duke-international-society-for-cardiovascular-infectious-diseases-diagnostic-criteria-for-infective-endocarditis/update