Abstract: As environmental concerns in tourist destinations become increasingly prominent, environmentally responsible behaviors (ERBs) of tourists have gained significant scholarly attention. Based on the Stimulus-Organism-Response (S-O-R) theory and taking Beijing Olympic Forest Park as an case study, this research employs an integrated approach combining Structural Equation Modeling (SEM) and fuzzy set Qualitative Comparative Analysis (fsQCA) to explore both the influence mechanisms and configurational patterns between tourist-companion interaction and ERBs. The results show that: ① Both dimensions of tourist-companion interaction (care and information sharing) significantly influence ERBs; ② Tourist experience and tourist satisfaction serve as important mediators in this relationship; ③Two distinct ERB formation patterns emerge—social interaction-driven and experience satisfaction-driven modes, suggesting ERBs result from both individual factors and their synergistic combinations. This study advances current understanding by elucidating the "black box" mechanism linking tourist-companion interactions to ERBs, contributes to the theoretical framework of ERB formation, and offers practical insights for developing environmentally sustainable tourism through fostering eco-conscious visitors.