 The study aimed to validate the Portuguese version of the Hoge Co-Anxiety Scale, HES, in young adults and examine the associations among eco-anxiety, socio-demographic characteristics, and pro-environmental behaviors. The results showed that the factorial structure of the original scale was replicated in the Portuguese version of the HES, showing good internal consistency, reliability over time, and strict invariance between men and women. A higher paternal education level predicted greater eco-anxiety in children. Two dimensions of eco-anxiety, namely, rumination and anxiety about personal impacts on the environment, predicted higher engagement in pro-environmental behaviors. The translated scale is an appropriate tool to measure eco-anxiety in the Portuguese context and should be used to collect evidence to drive environmental and health policies. Importantly, eco-anxiety can act as a protective emotional response to preserving the planet. This article was authored by Francisco Sampao, Tiago Costa, Luisa Teixeira Santos, and others.