Online abuse has emerged as a huge problem across the Internet and especially on social networking sites (SNSs). To combat this unacceptable online behavior, many SNS providers begin to implement built-in reporting functions/systems on their platforms. However, the effectiveness of this new function on SNSs depends on users' willingness to adopt and use. Thus, the main objective of this study is to identify the factors driving people to use the built-in reporting functions on SNSs. Drawing upon Theory of Cognitive Appraisal and the literature of social appraisal, we identified three major appraisal processes related to the use of online reporting functions on SNSs: primary appraisal (perceived emergency and perceived responsibility), secondary appraisal (perceived usefulness and perceived ease of use) and social appraisal (evaluation apprehension). We tested our research model with 117 Facebook users. Our findings suggest that perceived responsibility of the incident and perceived usefulness of the reporting functions are important factors promoting the use of built-in online reporting functions, whereas evaluation apprehension is an obstructing social factor to the use of built-in reporting functions. We expect that the results of this study make significant contributions to research and practice.