Introduction: During a health crisis, there are many challenges involved in communicating with the general public, with the ultimate goal of ensuring that as many people as possible follow preventive measures. Objective: The objective of this article is to present the results of an evaluation of the COVID-19 communication tools deployed by Santé publique France for the general public in March 2020. Two studies, one quantitative and one qualitative, were conducted during the first lockdown. The “Coronavirus Alert” communication campaign at that time consisted of four media formats (TV spots and posters) describing preventive measures and the symptoms of the disease. Results: Recall of the campaign was particularly high: nine out of ten people spontaneously cited messages from this campaign. More than 90% found it easy to understand or useful, although 20% considered it anxiety-inducing. The reported impact on behavior was also very high, with 97% of people stating they were encouraged to follow preventive measures. However, lower engagement with the campaign was observed among men and lower-income groups. The qualitative study helped explain some of the results: the clarity of the materials was attributed to the pictograms illustrating the protective measures, and the tone of the spots was deemed appropriate for the severity of the health situation. Conclusion: These studies highlight high exposure to the tested materials and a positive perception of them. Their findings have been useful for continuing the dissemination of prevention tools produced by Santé publique France.