Online social media is playing an important role in marketing. Word-of-mouth is one of the concepts that companies made use of. The gigantic social network in social networking sites helps companies disseminate promotional messages in a cost-effective and efficient way. Two of the antecedents of eWOM response in Facebook are discussed in this study, message source credibility and message appeal. A conceptual framework including these two eWOM antecedents in Facebook was developed and tested. 203 questionnaires were collected for verifying the conceptual framework. Data collected were then tested using structural equation modeling. As the concepts of message source credibility, message appeal and eWOM response are latent, a total of 8 measurement items were defined before the commencement of data collection. The findings show that message source credibility and message appeal have a positive impact on users’ intention to give eWOM response, in which the former has a greater impact on eWOM response.