["Applied Psychology: Health and Well-Being, Volume 18, Issue 3, June 2026. ", "\nAbstract\nThis paper systematically reviews the literature on levels of eco‐emotions reported by young adults (aged 18–29) across nations, with meta‐analyses of associations between eco‐anxiety and mental health outcomes. Fourteen databases were searched for relevant studies. Fifty‐nine studies reported levels of eco‐emotions, with 37 studies reporting associations between eco‐anxiety and each of anxiety, depression, and stress. Eco‐anxiety was the most reported eco‐emotion. Higher scores of eco‐anxiety and eco‐fear were reported by populations facing direct environmental impacts. Eco‐anger and eco‐hope were reported to have a role in adaptive coping. Meta‐analyses indicated moderate, significant positive associations between eco‐anxiety and depression r = 0.29, anxiety r = 0.34, and stress r = 0.30. Meta‐regressions were conducted to explore heterogeneity. Our results highlight the importance of addressing heterogeneity in operationalizing the construct of eco‐anxiety and the need to collect data on eco‐emotions in low‐and‐middle‐income nations, which is lacking in the current literature.\n"]