Since marketers and advertisers associate social media as an essential part of promotional mix, precise examination of the determinants that influence consumers’ engagement in online word of mouth via social media became crucial. This study employed the social capital theory to examine antecedents of in electronic word of mouth (eWOM) in the context of social networking sites. Based on survey data from 238 university students, online word of mouth was measured with three dimensions: opinion-giving, opinion-seeking and opinion-passing, using Partial Least Squares (PLS). The results identified tie strength and innovativeness as significant factors influencing eWOM behavior. Contrary to the original hypotheses – trust and shared language – were found not to be significantly related to online word of mouth. Also, no moderating effects by voluntary self-disclosure and innovativeness. This study suggests that eWOM behavior in social networks is unique by its nature with important social implications. Theoretical implications of the findings and future research directions are discussed.

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