This study investigated how sense of community and the perceived usefulness of word-of-mouth (WOM) information affect WOM effectiveness in an online community environment, and explored the roles of interactivity and site reputation as antecedent factors that can enhance sense of community and the perceived usefulness of WOM information. Additionally, this study sought to examine how the research model differs according to the receiver's need for cognition characteristics, which have been inadequately addressed in prior research. To summarize the research findings: First, sense of community and perceived WOM usefulness were found to have a direct effect on WOM effectiveness. Second, interactivity and site reputation were found to have positive effects on enhancing sense of community and WOM usefulness. Interactivity had the greatest impact on sense of community, while site reputation had a direct effect on WOM usefulness and WOM effectiveness. Third, the strength of the causal relationships among the factors influencing WOM effectiveness differed according to the WOM recipient's need for cognition characteristics. In particular, the direct effect of site reputation on WOM effectiveness appeared only in the group with low need for cognition, whereas in the group with high need for cognition, site reputation affected WOM effectiveness indirectly through perceived WOM usefulness. Finally, this study found that an individual's level of sense of community did not have a direct effect on perceived WOM usefulness, which represents the validity and credibility of WOM. Follow-up research should analyze how antecedent variables of WOM effectiveness operate according to the direction of WOM, and efforts should be made to analyze the role of WOM according to stages of purchase decision-making, set WOM objectives appropriate to product characteristics (e.g., involvement), and measure performance accordingly.