Background: In France, the number of admissions to emergency departments doubled between 1996 and 2016, leading to overcrowding. To cope with the resultant overcrowding, redirecting patients to new healthcare services is a viable solution, to spread demand more evenly across available healthcare delivery points, and render care more efficient. The goal of this study was to analyse the impact of opening new unscheduled care services on variations in patient attendance at a large emergency department. Methods: We performed a before-and-after study investigating the use of unscheduled care services in the Aube Department (Eastern France), focusing on emergency department attendance of Troyes Hospital. We applied a hierarchical clustering based on co-occurrence of diagnoses, to divide the population into different multimorbidity profiles and study their temporal trends. A multivariate logistic regression model was constructed to adjust the period effect for appropriate confounders. Results: In total, 120,718 visits to the emergency department were recorded over a 24-month period (2018-2019), and 14 clusters were identified accounting for 94.76% of all visits. The before-and-after analysis showed a decrease of 57.95 visits per week in 7 specific clusters, while the consumption of unscheduled health care services increased by 328.12 visits per week.Conclusions: Using an innovative and reliable methodology to evaluate changes in patient flow through the emergency department, our results could help to inform public health policy regarding the implementation of unscheduled care services, to ease pressure on emergency departments.