User-generated content (UGC) has become an important part of travel planning, as travelers evaluate travel products based on past reviews. However, different factors account for why tourists utilize UGC. The aim of this study is to review extant studies on UGC to identify the antecedents of UGC utilization for travel planning and the theories, models, and frameworks used in these studies. A total of 54 studies from 2005 to 2016 were found. This study found that UGC adoption is determined by attributes relating to the user, the source, the content, and response variables. It also found distinct and heterogeneous theories and frameworks mainly drawn from the information systems, socio-psychology, and management disciplines. Among the antecedents, the average path coefficients of the extracted relationships show that trust predicted attitude more than the other variables. Implications and future research directions are provided.