As marketers have integrated social media, especially social networking sites (SNS), as an essential part of advertising and marketing strategies, insights into factors influencing consumers' eWOM engagement via SNS is becoming important. This research investigated factors influencing consumer eWOM on SNS in Malaysia. The research sample consisted of 291 respondents with active account for at least one of these SNS (Facebook, Twitter, YouTube and Instagram). Multiple regression analysis was used and the research findings confirmed that Trust in contacts on SNS, Involvement in SNS and Perceived Usefulness respectively have positive influence on customers' engagement in eWOM via SNS. This study concludes that eWOM via SNS as an emerging marketing tools is significant with substantial social implications. Accordingly, the discussion of findings, implication and recommendations for online marketers, firms and academician/researchers were discussed.