The purpose of this study is to empirically Investigate the critical success factors affecting the participation of B2B e-marketplace from a perspective of buyers and sellers. The research model presented in this study suggests that the success of B2B e-marketplace depends on the degree of participation of buyers and sellers. It is hypothesized that the participation of buyers and sellers is related with several contextual factors. The contextual factors included: (a) industry and market factor; (b) Internal environment factor; (c) product factor; (d) Inter-organizational factor; and (e) B2B e-marketplace system and strategy factor. An analysis of data from 31 buyer firms and 31 seller firms reveals that those five factors have a significant effect on the participation and success of B2B e-marketplace. The implications of the study are discussed and further research directions are proposed.