Diagnostic errors (DEs), which encompass failures of accuracy, timeliness, or patient communication, cause appreciable morbidity but are understudied in pediatrics. Pediatricians have expressed interest in reducing high-frequency/subacute DEs, but their epidemiology remains unknown. The objective of this study was to investigate the frequency of two high-frequency/subacute DEs and one missed opportunity for diagnosis (MOD) in primary care pediatrics.