Recent studies suggest that eco-anxiety motivates pro-environmental behaviors. However, these studies are all cross-sectional in nature, and they frequently neglect possible important confounding variables (e.g., ecological identity). The present study was designed to deepen our understanding of the effect of eco-anxiety on pro-environmental behaviors by addressing the abovementioned limitations of recent research. The present study consisted of a 2-wave longitudinal study in which eco-anxiety and pro-environmental behaviors as well as possible confounding variables (i.e., ecological identity and personality) were assessed among French adults. As hypothesized, individuals' experience of eco-anxiety at t1 was positively and significantly related to individuals' engagement in pro-environmental behaviors at t2. This significant positive relationship was observed even when ecological identity, the Big Five domains of personality, and proenvironmental behaviors at t1 were controlled for. It thus appeared that compared with individuals with low levels of eco-anxiety at a given time, individuals with higher levels of eco-anxiety at a given time displayed a greater likelihood of experiencing increases in their subsequent engagement in pro-environmental behaviors. The results are discussed in light of current knowledge about the function of anxiety.