With the continuous development of the internet and e-commerce in Vietnam recently, there is much research on online purchasing behaviors through retail websites. However, there are few studies on consumers’ purchasing behavior via social network sites (SNS) despite a rapid increase in the use of such websites. This study, therefore, tries to build a research model describing (i) the impact of motivations of using SNSs on social e-WOM and (ii) the relationship among social e-WOM, consumers’ trust, attitude and purchasing intention via SNSs. After adjusting the measurement scales by a focus group’s discussion, a quantitative survey was executed using the data collected from 509 SNS users and by testing Cronbach’s Alpha reliability, EFA, CFA, and SEM to comment seven proposed hypotheses. The results showed that motivations of social media usage (utilitarian and hedonic) had positively impacted on social e-WOW, social e-WOW influenced positively consumers’ trust and attitude towards brands of goods/service on SNSs, and that both consumers’ trust and attitude had positive impacts on their purchasing intention. Accordingly, the study suggested some practical implications for managers to adjust their social communication strategies in the digital era.