While relationships are crucial in conducting collaborative commerce (c-commerce), there has been very little c-commerce research on this topic. This study aims to explore the determinants and effects of relationships in c-commerce using the case study method. The study results of four Taiwanese enterprises indicate that the quality of relationship is not correlated with the closeness of the relationship. Furthermore, organizational culture, resource dependency and collaborative technology are the main determinants of collaborative relationships. Good organizational culture, deeper resource dependency and higher application of collaborative technology would facilitate the development of collaborative relationships. Finally, collaborative relationships will affect performances; however, in highly uncertain environments, the influence of collaborative relationships on performances may not be significant. This study reveals how a collaborative relationship forms and acts in c-commerce, which provides a new perspective for further research and can be applied in practice to achieve successful c-commerce through managing collaborative management effectively.