This is a timely study that simultaneously considers the issues of source credibility of social media contents and generational differences. The study aims to explore the influence of ‘generation’ on perceived source credibility, and its effect on the relation between source credibility, hotel brand image, and purchase intention in cases where the content providers are general users (UGCs) and hotel marketers (MGCs), respectively. Using an independent samples t-test (278 people sampled), the differences in source credibility between generations were tested and multi-group analysis was conducted to verify the moderating effect of generation. Significant differences appeared in trustworthiness between the generations. Millennials are sharper in observation than the generations born earlier in recognizing the source credibility of social media contents. The moderating effect of generation is noticeable only in the impact of the UGCs’ expertise on hotel brand image, indicating Millennials are affected by the expertise of UGCs more strongly than the earlier generations are. The findings offer insight into better strategizing of social media communication for hotel marketers, utilizing social media and targeting Millennials. A further contribution of the study is that it reveals the relations between variables and effects according to different content providers (UGCs and MGCs).