Vital signs can help clinicians identify children at risk of serious illness. The NICE guideline for fever in under-fives recommends a routine measurement of temperature, heart rate, capillary refill and respiratory rate in all febrile children visiting the emergency department (ED). This study aims to evaluate the measurement of paediatric vital signs in European EDs, with specific attention to adherence to this NICE guideline recommendation. In a prospective observational study, we included 4560 febrile children under 16 years from the ED of 28 hospitals in 11 European countries (2014-2016). Hospitals were academic (n = 17), teaching (n = 10) and non-teaching (n = 1) and ranged in annual paediatric ED visits from 2700 to 88,000. Fifty-four percent were male, their median age was 2.4 years (IQR 1.1-4.7). Temperature was measured most frequently (97%), followed by capillary refill (86%), heart rate (73%), saturation (56%) and respiratory rate (51%). In children under five (n = 3505), a complete measurement of the four NICE-recommended vital signs was performed in 48% of patients. Children under 1 year of age, those with an urgent triage level and with respiratory infections had a higher likelihood of undergoing complete measurements. After adjustment for these factors, variability between countries remained. Conclusion: Measuring vital signs in children with fever in the ED occurs with a high degree of practice variation between different European hospitals, and adherence to the NICE recommendation is moderate. Our study is essential as a benchmark for current clinical practice, in order to tailor implementation strategies to different European settings.What is Known:• Vital signs can quickly provide information on disease severity in children in the emergency department (ED), and the NICE guideline for fever in under-fives recommends to routinely measure temperature, heart rate, capillary refill and respiratory rate.• Data regarding measurement of vital signs in routine practice across European EDs is currently unavailable.What is New:• Measurement of vital signs in febrile children is highly variable across European EDs and across patient subgroups, and compliance to the NICE recommendation is <50%.• Children under 1 year of age, those with an urgent triage level and with respiratory infections had a higher likelihood of undergoing complete measurements.