Introduction. Changes in Public Health recommendations may have changed the number of emergency visits and COVID-19 diagnosed cases in an Emergency Department in Madrid. Material and methods. This retrospective case series study included all consecutive patients in a tertiary and urban ED in Madrid from 1st to 31st March. The sample was divided: NonCOVID-19, Non-investigated COVID-19, Possible COVID-19, Probable COVID-19, Confirmed COVID-19. Differences between public health periods were tested by ANOVA for each cohort, and by ANCOVA including the number of PCR tests (%) as covariate. Results. A total of 7,163 (4,071 Non-COVID-19, 563 Non-investigated COVID-19, 870 Possible, 648 Probable and 1,011 Confirmed COVID-19) cases were included. Public Health measurements applied during each period showed a clear effect on the case proportion for the five cohorts. Conclusion. The variability of case definitions and diagnostic test criteria may have impact on the number of emergency visits and COVID-19 diagnosed cases in Emergency Department.