<p>Rapid growth in nature-based tourism is increasing pressure on fragile environments and highlighting a persistent gap between tourists’ pro-environmental intentions and their reported on-site behavior. This study examines green mindfulness as an attentional construct associated with sustainable tourist behavior in tourism settings where visitors must interpret environmental cues in real time. Using cross-sectional survey data collected from 500 domestic and international visitors across selected tourism sites in Vietnam and analyzed with structural equation modeling, the study assesses how individual predispositions, service-provider mechanisms, and contextual cues are associated with green mindfulness. Results show that contextual cues are the strongest predictors of green mindfulness, while habitual consumption lowers mindful awareness. Green mindfulness significantly predicts sustainable tourist behavior and is associated with indirect relationships between selected antecedents and reported behavior. The findings contribute to research on sustainable tourism by showing how attentional processes may complement Value-Belief-Norm reasoning in dynamic tourism environments, while also highlighting the limits of cross-sectional self-reported evidence.</p>