Background: “A wildfire is a fire that spreads freely through vegetation with undesirable effects on vegetation. Predictions indicate that the effects of climate change will cause the rate of forest fires to increase by 50% by the end of 2100, and that these fires will become increasingly frequent in areas where they did not previously occur, such as in the Arctic. Spain accounts for almost 40 percent (39.39%) of the total number of hectares burned in 2022 in the European Union, with 236,575 of the 600,731 hectares burned, according to data from the European Commission’s Copernicus European Fire Information System (EFFIS). The objectives of the present study were: a) to analyze the levels of stress present during a working day of forest firefighters when they did not carry out any firefighting operations and b) to analyze the level of agreement between the selected physiological and perceived stress assessment instruments.Results: In general, the average total stress analyzed during a working day without an extinguishing operation shows low or very low stress balance (physiological stress) levels, closer to 0, and stress perception (psychological stress) levels also categorized as “low stress”.Conclusions: According to the results obtained, the level of physiological and self-perceived stress is moderate. The female gender is more stressed. The higher the age and experience, the lower the stress level. The study instruments used are valid for a quick and reliable measurement of stress levels.