This study examines the relationship between environmental attitudes, outdoor recreation motivations, and environmentally responsible behaviors. Little has been reported about whether motivation can serve as a mediator to better understand environmental attitude–behavior relationships. On-site responses collected from Florida National Scenic Trail hikers were utilized in a structural equation model. Structural model results indicated significant relationships between attitudes, motivations, and behaviors. Environmental attitudes influenced motivations and environmental behaviors, and motivations were significantly related to environmental behaviors. Further analyses found that motivation served as a partial mediator of the attitude–behavior linkage. These results suggest that environmental attitudes and motivations substantially shape environmentally responsible behaviors. Managerial implications are discussed, including maintaining natural aspects of environments and increasing awareness about natural environments through educational programs. Further studies utilizing participants in other outdoor recreation activities at various settings are recommended.