With social media becoming the primary channel for travelers to acquire travel-related information, tourism service providers are increasingly partnering with social media influencers (SMIs) as part of their digital marketing strategy. The present study investigates the effectiveness of SMIs by examining the role that two message factors—argument quality and sponsorship status—have on travelers’ perceptions of a hotel’s commitment to sustainability and their intention to stay at the hotel. Results from four studies show that when eco-friendly hotels sponsor SMIs, an attribute-value message is more effective than a simple recommendation message in influencing travelers’ perceptions and intentions. Given the latest Federal Trade Commission regulations regarding sponsorship disclosure practices, the findings offer valuable insights for tourism providers using SMIs. The study findings suggest that SMIs should create sponsored messages that provide rational and objective information about the hotel’s sustainability practices to stimulate travelers’ related cognitions and persuade them to patronize the hotel.