Background The tourism industry’s growth and environmental impact have prompted the need for sustainable tourism models. With the rising popularity of natural ecotourism in Indonesia, there are concerns about waste generation and environmental damage caused by tourists’ behavior, particularly littering. Focus of the Article This study employs the Theory of Planned Behavior (TPB) to understand the psychological factors influencing tourists’ intentions not to litter at natural tourism destinations. Research Question/Hypotheses This study investigates what influences tourists’ intentions and behavior not to litter. It hypothesizes that experiential attitude, instrumental attitude, injunctive norm, descriptive norm, and perceived behavioral control significantly affect intentions and examines the relationship between perceived behavioral control, intention, and actual behavior. Importance to the Social Marketing Field This study contributes by differentiating two key aspects in the constructs’ attitude, experiential and instrumental, toward behavior and subjective norm of tourists’ intention not to litter. This study provides insights into tourists’ littering behavior, aiding social marketing strategies for sustainable tourism in natural destinations. Methods A study at the Bogor Botanical Garden in Indonesia surveyed 400 respondents. A combination of structural equation modeling (SEM), confirmatory factor analysis (CFA), discriminant validity analysis, and goodness-of-fit (GoF) tests was used for the data analysis using LISREL 8.8. Results The study findings confirm and support all hypotheses, demonstrating that both affective and instrumental attitudes significantly influence intentions not to litter. Additionally, injunctive and descriptive norms play crucial roles in shaping these intentions, while perceived behavioral control significantly impacts both intentions and actual behavior. Recommendations for Research or Practice These findings suggest emphasizing instrumental attitudes is crucial for designing social marketing strategies to promote responsible behavior and environmental sustainability in natural tourism destinations.