PurposeThe purpose of this study is to contribute to the existing knowledge on two aspects. First, the authors introduce a conceptual model based on the social capital theory (SCT) to understand the mechanisms through which social capital factors affect consumers’ electronic word-of-mouth (eWOM) engagement and purchase intentions via social network sites (SNSs). Second, the present study empirically tests and validates the proposed relationships that delineate social capital dimensions as crucial precursors of eWOM engagement and purchase intention in the specific SNS context, namely, Facebook, Instagram and Twitter.Design/methodology/approachThe authors applied both exploratory and descriptive design based on a triangulation approach. The authors adapted an in-depth interview method in the first part to better specify our constructs and hypotheses. At the quantitative part, the authors conducted the survey method on 1,169 consumers as central part of the research for empirical testing and validating our conceptual model. The authors applied structural equation modeling analysis by using AMOS 22.0.FindingsOverall, the results of this study indicate that social capital-based drivers have a significant role underlying the eWOM engagement of consumers, while engagement in eWOM has a further effect on their purchase intentions. In this study, social network culture appears as the most dominant social driver of consumers’ engagement in eWOM, followed by tie strength and interpersonal trust.Research limitations/implicationsThis study extends prior research on drivers of eWOM. An integrated conceptual model under SCT is proposed and tested to verify the dimensional interrelationships and effects on consumers’ eWOM engagement and purchase intentions. Second, this work advances the understanding of eWOM behavior in a novel context, social networks. Cross-cultural comparison of our results in other regions of Turkey or different countries might enable generalizability, which is one of the limitations of the study.Practical implicationsThis study highlights that consumers are incorporating recommendations into their social networking behavior. The findings of this study show that before constructing their social media strategies, marketers should first investigate the congruence between the cultural environment of the SNS in which they connect with their customers and the positioning of their products.Social implicationsThis study suggests implications about privacy guidelines for SNS regulation setters. Policymakers should understand when and how consumers’ profile and social tie information should be disclosed and accessed through their eWOM behaviors and try to develop trustful regulations.Originality/valueThis study serves as the first attempt to demonstrate that social capital drivers affect consumers’ purchase intentions through their eWOM engagement by its robust conceptual model. No integrated model under SCT has ever been proposed and tested on consumers’ eWOM engagement via SNSs.