Following the paradigm of social network analysis, the research tackles the individual-level social contagion effect in the new product adoption process, and tests the varied impact of two heterogenous forms of social capital on new product adoption from the perspectives of the influencer’s influence, the adopter’s susceptibility and characteristics of the relationship between the influencer and adopter. Based on the real-world data from an online word-of-mouth website, an empirical analysis demonstrates that bridging social capital has a positive effect on both influence and susceptibility, and bonding social capital has no direct effect on susceptibility. Both forms of social capital are complementary in their interactive impact on influence but substitutable on susceptibility. After controlling the effect of selection bias, homophily between consumers and marketing efforts of the firms, the analysis results are still robust.