Interruptions in the Emergency Department (ED) are moderately studied in regard to their impact on physicians’ workload. This study captured interruptions characteristics and measures of workload. Twenty-eight ED physicians were followed during their shifts; interruptions they faced were captured using a validated tablet PC-based tool. At the mid and end of their shift, providers completed a NASA-Task Load Index (TLX) questionnaire and a reaction time task. Descriptive statistics and ANOVA were used to identify relationships between physicians’ interruptions and workload. A total of 2355 interruptions were identified ( M =84.1, SD =14.5). The NASA-TLX results showed increase in physicians’ responses for all subscales from mid to end-shifts. Reaction time was higher at end-shift with mean difference of 33.75ms, 95% CI [20.35, 47.13], p < 0.001. At end-shift, there was a statistically significant positive correlation between reaction time and all NASA-TLX subscales. Interruption duration rather than frequency correlated positively with NASA-TLX scores. High/critical interruptions were the least frequent but had longer duration and greater impact on workload. This study provided a unique examination of interruptions over an entire provider shift and identified interruptions as potential causes of increased workload for ED physicians.