A major industrial fire broke out in Rouen on September 26, 2019, at the Lubrizol and NL Logistique sites. Santé publique France established the “Santé post Incendie 76” initiative to conduct a comprehensive assessment of the accident’s health consequences for the exposed population. This report presents the main results of the cross-sectional survey conducted as part of this initiative, whose primary objective was to study the short- and medium-term health impacts of the accident (one year later). The study was conducted on a representative sample of the 340,000 residents of 122 municipalities in Seine-Maritime (76) exposed to the accident. Data were collected via questionnaire in September and October 2020 from 3,764 adults and 1,029 children in the exposed area, and from 1,015 adults and 208 children representing the population of Le Havre and its surroundings (control area). During the fire and its aftermath, a large proportion (92%) of the population in the exposed area perceived at least one of the accidental pollutants: noise, flames and explosions, black smoke, odorous substances, soot, and pieces of fiber-cement roofing material deposited on the ground. The perception of odors, in particular, could persist for a long time and be bothersome. It was observed that 66% of people reported at least one health issue attributed to the accident. These were primarily psychological, otolaryngological (ENT), general, ocular, respiratory, and sleep-related symptoms. Residents living near the site of the disaster reported more symptoms and health problems than those living further away. Two-thirds of symptomatic adults did not seek medical care; the others primarily consulted a general practitioner or self-medicated. Several perceived exposures (odors, black smoke, soot deposits, and having been awakened, seen, or heard the fire) are statistically linked to the symptoms most frequently experienced by adults in the aftermath of the accident and to the use of medical and psychological care. The strongest association was observed with the perception of odors, particularly regarding ENT disorders and headaches, and a growing relationship was identified between the duration of olfactory exposure and the main reported health events. Among children, the health complaints experienced and their frequencies, as well as the reported use of healthcare services, were comparable to those of adults. One year later, this accidental event had a negative effect on the perceived health of residents in the exposed area, as measured by the 12-item version of the Medical Outcomes Study Short Form Health Survey (SF-12), particularly on their mental health. The number of perceived nuisances, the perception of odors—especially when prolonged—soot deposits around the home, and having seen, heard, or been awakened by the fire were associated with impaired mental health. The results of this study are consistent with data collected in the aftermath of the accident by other means, and with the epidemiological literature addressing the health effects of exposure to pollution and nuisances and the psychological consequences of similar accidental events. The industrial fire of September 26, 2019, had an overall effect on perceived health that was still measurable one year later, underscoring the importance of establishing a prospective post-accident health monitoring program for the exposed population. These observations allow for initial proposals for action aimed at improving the management of the health consequences of this fire and the preparation of the response to future industrial accidents.