Sustainability has emerged as a critical concern in the tourism industry. In sustainable tourism, the question of how to engage tourists in value co-creation has started to receive attention. Based on service-dominant logic, this paper develops an integrated model to reveal the impact of tourist operant resources on online citizenship behavior from the perspective of interactions between tourists and online travel agencies (OTAs). Empirical research is conducted using data collected from 301 tourists with customized sustainable tourism experiences. The results show that tourist operant resources are positively associated with online citizenship behavior, with the perceived value (functional value and emotional value) playing a partially mediating role in this relationship. Knowledge distance between tourists and OTA service personnel exerts an inverted U-shaped moderating effect on the relationship between tourist operant resources and functional values, but it does not have a moderating effect on the relationship between tourist operant resources and emotional values. Resource integration capability positively moderates the impact of tourist operant resources on functional and emotional values. This study reveals the contingency role of tourist operant resources in the entire value co-creation process in the context of sustainable tourism and provides practical guidance for OTAs to promote tourists’ online citizenship behavior to develop sustainable tourism.