Background: The French syndromic surveillance (SyS) system, SurSaUD®, was one of the systems used to monitor the COVID-19 outbreak. Objective: This study described the epidemiological characteristics of COVID-19-related visits to both emergency departments (EDs) and the network of emergency general practitioners known as SOS Médecins (SOSMed) in France from February 17 to June 28, 2020. Methods: Data on all visits to 634 EDs and 60 SOSMed associations were collected daily. COVID-19-related visits were identified using ICD-10 codes after coding recommendations were sent to all ED and SOSMed doctors. The time course of COVID-19-related visits was described by age group and region. During the lockdown period, the characteristics of ED and SOSMed visits and hospitalizations following visits were described by age group and gender. The most frequent diagnoses associated with COVID-19-related visits were analyzed. Results: COVID-19 SyS was implemented on February 29 and March 4 for EDs and SOSMed, respectively. A total of 170,113 ED and 59,087 SOSMed visits related to COVID-19 were recorded, representing 4.0% and 5.6% of the overall coded activity, with a peak in late March accounting for 22.5% and 25% of all ED and SOSMed visits, respectively. COVID-19-related visits were most frequently reported among women and those aged 15–64 years, although patients who were subsequently hospitalized were more often men and individuals aged 65 years and older. Conclusion: SyS enabled population-level health monitoring of the COVID-19 epidemic in France. As SyS has more than 15 years of historical data characterized by high quality and reliability, it was considered sufficiently robust to contribute to defining the post-lockdown strategy.