The purpose of this study is to empirically examine the effect of gamification on tourist psychological outcome and knowledge gain in the context of cultural heritage sites, which are popular cruise tourism destinations. A comprehensive literature review revealed the critical role of gamification in facilitating psychological (enjoyment, flow experience, and loyalty) and behavioral outcomes (knowledge gain) at cultural heritage sites. Using a field experiment, this study employed a gamified app as a manipulation. A total of 342 gamified app users (n = 165) or non-users (n = 177) were selected by stratified random sampling method from among college students majoring in tourism and cruise management in South Korea. After screening the data, a Hayes' PROCESS modeling technique was mainly utilized to test the proposed hypotheses based on 331 cases. The results showed that gamification had a strong influence on knowledge gain about cultural heritage attractions. On the other hand, gamification had negative effects on enjoyment and flow experience. More importantly, gamification had a negative indirect effect on loyalty toward cultural heritage attractions. These findings imply the usefulness of gamified apps to convey memorable and real-time information and knowledge to users in cultural heritage sites.