This study presents a critical literature review on the tourist attitude–behavior gap and intention–behavior gap in sustainable tourism research and proposes future research directions. A systematic review was conducted using preferred reporting items for systematic review and meta-analysis (PRISMA) on the existing literature from the Scopus and Web of Science databases. Key research topics in attitude–behavior gaps are the role of environmental knowledge, protected area management, the role of service quality, risk perception, moral licensing, sustainability communication, business owners in tourism, environmental concern, tourist psychology, and intervention. Key research topics in the intention–behavior gaps of sustainable tourism are green certification or label, value, rationality and social desirability, motivation, trust, inconvenience, and quality. Four emerging research trends were discovered in recent years: (1) increased use of mixed methods and surveys; (2) consideration of green or environmental knowledge; (3) role of green certification; and (4) consideration of tourist moral values. Recommended future research directions include theoretical development studies in the hospitality sector, cross-cultural comparisons, investigation, of under-researched tourism sectors, and new research methodologies. This review provides an overview of research on the attitude–behavior gap and the intention–behavior gap in sustainable tourism. Our study proposes a new framework for the attitude–behavior gap and the intention–behavior gap, departing from the theory of planned behavior. We identify direct and indirect factors that influence sustainable tourist behavior, with sustainable tourist attitude and intention serving as mediators. Overall, our findings offer valuable insights into the complex relationship between attitudes, intentions, and behaviors in sustainable tourism.