Abstract Background Climate change poses serious challenges to Public Health, including mental health impacts. In Italy, few studies investigated the rise of eco-anxiety, especially among adolescents, who are the main group affected by this feeling. Specific measurement tools for this population are needed to fill this gap. The aim is to adapt the Italian version of the Climate Change Anxiety Scale (CCAS) to adolescents, and pair it with a socioeconomic and demographic questionnaire (SDQ) to assess determinants. Methods The Italian CCAS was modified for adolescents through a process involving a literature review, expert discussions, and a pretest. This adapted version (a-CCAS) was tested with individuals aged 14-18 years old, maintaining an ideal ratio of 10 respondents per item. Extant psychometric scales were utilized to assess its validity. The SDQ was developed from results of a systematic review of known associations between socioeconomic and demographic factors and eco-anxiety in youth, and expert discussions, and validated by piloting the SDQ with another sample of adolescents. Internal consistency of the a-CCAS and SDQ was assessed by Cronbach’s alpha (Cα). Results The a-CCAS kept most of its original content, comprising 13 items and 2 subscales: cognitive and functional impairment. Pilot respondents were 162; Cα coefficient was >0.7 for both subscales. Convergent and concurrent validity showed positive correlations with the extant scales. The SDQ comprised 12 items in 3 domains: family, social and political-environmental determinants. Respondents were 47 and Cα coefficient was >0.7. Conclusions The a-CCAS and SDQ are valid tools for assessing baseline eco-anxiety and its determinants in Italian adolescents and can contribute to Public Health efforts to reduce the climate-related mental health burden, by measuring the impact of specific educational interventions about climate change targeted at the young. This questionnaire was created as part of the PRIN P2022JJ3LB project. Key messages • These results contribute to filling an evidence gap on eco-anxiety and its socioeconomic and demographic determinants among Italian adolescents by providing researchers with a valid measurement tool. • This tool holds promise for assessing the impact of psychologically-informed educational interventions about climate change and adaptive coping strategies on adolescents’ eco-anxiety levels.