A longitudinal experience-sampling study of 1,341 participants from 17 European countries (total assessments = 44,894) tracked well-being levels during the weeks surrounding the Russian invasion of Ukraine on February 24, 2022. The study found a significant decline in well-being on the day of the invasion, with recovery over the following weeks associated with individual personality traits, particularly the meta-trait Stability. Individuals with lower Stability showed minimal recovery. Well-being was lower on days when the war was more salient on social media. The results indicate that the psychological impact of the war was widespread, with no significant association between well-being and age, gender, social status, or political orientation. The study also found that daily well-being was negatively associated with the salience of the war on social media, with higher salience correlating with lower well-being. These findings highlight the need to consider the psychological implications of the war alongside its humanitarian, economic, and ecological consequences. The study used international, longitudinal data to investigate the development of well-being during the weeks surrounding the invasion, potential explanations for individual differences in reactions, and the correspondence between daily well-being and the salience of the war on social media. The results suggest that the psychological effects of the war were complex, with recovery influenced by individual personality traits and the salience of the war on social media. The study also found that well-being was lower in European countries compared to non-European countries during the period surrounding the invasion. The findings underscore the importance of considering psychological well-being in addition to the immediate physical and economic impacts of the war.A longitudinal experience-sampling study of 1,341 participants from 17 European countries (total assessments = 44,894) tracked well-being levels during the weeks surrounding the Russian invasion of Ukraine on February 24, 2022. The study found a significant decline in well-being on the day of the invasion, with recovery over the following weeks associated with individual personality traits, particularly the meta-trait Stability. Individuals with lower Stability showed minimal recovery. Well-being was lower on days when the war was more salient on social media. The results indicate that the psychological impact of the war was widespread, with no significant association between well-being and age, gender, social status, or political orientation. The study also found that daily well-being was negatively associated with the salience of the war on social media, with higher salience correlating with lower well-being. These findings highlight the need to consider the psychological implications of the war alongside its humanitarian, economic, and ecological consequences. The study used international, longitudinal data to investigate the development of well-being during the weeks surrounding the invasion, potential explanations for individual differences in reactions, and the correspondence between daily well-being and the salience of the war on social media. The results suggest that the psychological effects of the war were complex, with recovery influenced by individual personality traits and the salience of the war on social media. The study also found that well-being was lower in European countries compared to non-European countries during the period surrounding the invasion. The findings underscore the importance of considering psychological well-being in addition to the immediate physical and economic impacts of the war.