Grounded on the social embeddedness approach, this article aims to analyze how entrepreneurs mobilize relationships to access resources in the set-up and evolution of new ventures. Based on the conceptualization of entrepreneurship as an evolutionary process, we developed a comparative case study of two high-technology firms that participated in incubators through face-to-face, in-depth interviews with the founders as well as with the actors that represented their main relationships during the existence of the firms. In terms of data analysis, we divided up the trajectories of the firms into three phases dubbed pre-incubation, incubation and graduation as well as categorized the resources accessed in each phase. Based on this, we found out that the entrepreneurs mobilized their main relationships to access simple and complex resources in the set-up phase. However, in the phase of evolution, the mobilization of these relationships was contingent on the degree of complexity of resources.