This chapter introduces e-marketplace adoption success factors as a challenge and opportunity for a small developing country. The chapter offers insights into e-marketplace definitions with e-marketplaces’ business models and business processes. Further it describes opportunities for, and threats to e-marketplaces’ use. Success factors of e-marketplace adoption are divided into three groups: organizational factors, e-marketplace factors and environmental factors. The authors argue that each of these group influences significantly an organization’s e-readiness for e-marketplace adoption. The importance of each of these factors is described on the basis of the results of research, conducted in 119 large organizations in Slovenia. Furthermore, the authors believe that by understanding these factors, organizations will be able to prepare better for successful e-marketplace adoption and successfully exploit important competitive advantages offered by new e-commerce business models.