Objective: The aim of this study was to describe the impact of additional medical specialists, non-emergency physicians (non-EPs), performing direct supervision or a combination of direct and indirect supervision at an EP-led emergency department (ED), on patient flow and satisfaction. Patients and methods: An observational, cross-sectional, three-part study was carried out including staff surveys (n=379), a before and after 16-week data collection using data of visits during the peak hours (n=5270), and patient questionnaires during 1 week before the pilot and during week 5 of the pilot. Content analysis and descriptive statistics were used for analyses. Results: The value of being present at the ED was acknowledged by medical specialists in 49% of their surveys and 35% of the EPs' and ED nurses' surveys, especially during busy shifts. Radiologists were most often (67.3%) convinced of their value of being on-site, which was agreed upon by the ED professionals. Perceived improved quality of care, shortening of length of stay, and enhanced peer consultation were mentioned most often. During the pilot period, length of stay of boarded patients decreased from 197 min (interquartile range: 121 min) to 181 min (interquartile range: 113 min, P=0.006), and patient recommendation scores increased from -15 to +20. Conclusion: Although limited by the mix of direct and indirect supervision, our results suggest a positive impact of additional medical specialists during busy shifts. Throughput of admitted patients and patient satisfaction improved during the pilot period. Whether these findings differ between direct supervision and combination of direct and indirect supervision by the medical specialists requires further investigation.@en