From November 30 to December 12, 2015, France hosted the 21st Conference of the Parties (COP21) on climate change. The conference was held primarily at the Paris-Le Bourget Exhibition Center in the department of Seine-Saint-Denis. The COP21 mission required that every instance of medical care provided under the health care system (established based on UN specifications) be recorded and that the interventions of health care teams be traceable. Healthcare coverage combined an emergency medical response system (SAMU and SMUR) with a pre-deployed emergency response unit. The Île-de-France Regional Health Agency requested the Île-de-France Regional Intervention Unit (CIRE) to analyze daily the interventions handled and assess the conference’s health impact on healthcare and emergency response capacity. Health monitoring was conducted using a single information system that tracked both the activity of first responders and SAMU teams at the COP21 site. This system identified 1,238 visits (with mostly minor reasons for consultation) involving 1,102 patients, and 34 medical transports were reported. While health monitoring helps identify high-risk situations or those requiring intervention, the event-specific care protocols entailed a significant data collection workload for first responders and the SAMU. The expected objectives of a shared information system for first responders and emergency physicians must be clarified in light of the reasons for seeking care typically observed.