Purpose The purpose of this study is to investigate the factors influencing green travel intentions within the tourism sector. By examining the moderating effect of green knowledge within the theory of reasoned goal pursuit (TRGP) framework, the research aims to enhance understanding of green travel decision-making and contribute to the development of strategies that promote sustainable travel practices in Vietnam and beyond. Design/methodology/approach Drawing upon the TRGP, a conceptual framework is developed to understand the relationships among active procurement goals, active approval goals, attitudes toward green travel, subject norms, green travel motivation, perceived behavioral control and green travel intention. The study adopts a quantitative research design and collects data from a sample of 544 Vietnamese tourists through a survey instrument. Findings The relationships between TRGP variables are discovered and confirmed in the context of ecotourism. Furthermore, the moderating roles of green knowledge are also investigated, directly contributing to sustainable tourism through the lens of TRGP. Research limitations/implications The study's exploration of green travel intention and the role of green knowledge contributes to theoretical frameworks and underscores the significance of environmental education in fostering sustainable travel behaviors. Stakeholders in the Vietnamese tourism sector can benefit from practical insights by focusing on eco-friendly accommodations and responsible tour packages. Leveraging social influence and educational campaigns may further encourage sustainable travel practices among Vietnamese tourists, enhancing their inclination toward environmentally conscious behaviors. Originality/value The research underscores the importance of interventions that target goal-oriented factors, positive attitudes, social norms, perceived control and green knowledge in molding sustainable travel behaviors. These insights provide a foundation for tourism stakeholders to tailor strategies such as environmental education programs and supportive policies to promote sustainable tourism practices among Vietnamese tourists effectively.