As an emerging group that wields its increasing influence through social media, social media influencers (SMIs) have continued to grow as a key component of firms’ digital marketing strategies. However, several aspects of SMIs merit attention: their personal characteristics, content features, and how they influence consumers’ decision-making as well as online engagement. By using the stimulus–organism–response (SOR) model together with theories of social connection and social influence, this dissertation reveals the influence of SMIs on consumer behaviors in tourism and hospitality contexts by investigating travel SMIs’ influencing stimuli, mechanisms, and audience responses. Study 1 extracts topics from comments on posts created by two travel SMIs from different cultures; identifies these SMIs’ personal characteristics and content features; and uncovers how travel SMIs wield social connection, value-expressive influence, and informational influence from a cross-cultural perspective. Study 2 includes a pair of sub-studies that quantitatively examine travel SMIs’ marketing effectiveness and unveil associated mechanisms by focusing on social influence theory (i.e., value-expressive and informational influences). Topic modeling, netnographic analysis with social media data, and experimental designs are adopted to achieve all research objectives. Findings extend the understanding of travel SMIs’ influencing processes in consumers’ decision making/online engagement and provide practical implications for applying SMI marketing in tourism and hospitality. / Tourism and Sport