The incidence of skin cancer continues to rise in Europe. The main risk factor is excessive exposure to ultraviolet (UV) radiation. The main objectives of our study are to estimate the frequency of sunscreen use in 2021, to explore the associated determinants, and to examine trends since 2005. This study is based on the 2021 Santé publique France Public Health Barometer survey. A sample of 24,514 people aged 18 to 85 residing in mainland France was selected between February and December 2021 through random generation of landline and mobile phone numbers. Respondents aged 18 to 75 were asked about their use of recommended sun protection measures on a sunny summer day, their knowledge, and two beliefs. Bivariate and multivariate analyses were weighted to account for selection probability and the structure of the population in France. The determinants and trends of the variables of interest were examined using univariate and multivariate Poisson regression. While the vast majority (84.8%) of 18- to 75-year-olds feel they are well informed about the potential negative health effects of sun exposure, only half (50.7%) know that the most dangerous hours for sun exposure are between noon and 4:00 p.m. in mainland France (a decline compared to 2015). “Wearing sunglasses ” (73.2%) is the most common form of protection used “systematically” or “often,” ahead of “staying in the shade” (72.2%), “avoiding the sunniest hours” (67.7%), “wearing a hat or cap” (56.1%), “applying sunscreen every 2 hours” (35.6%), or “wearing long-sleeved clothing” (27.2%). Men and people aged 18–24 are less likely to adopt these behaviors. Avoiding the sunniest hours between noon and 4 p.m., applying sunscreen every two hours, and wearing long-sleeved clothing have declined compared to 2005. The most effective sun protection measures are not consistently or frequently practiced. To reduce excessive exposure to UV rays in France, sun safety messages should be updated and better targeted at young people and men, drawing inspiration from prevention programs that include interventions proven to be effective.