This book chapter focuses on inter-organizational boundary-spanning activities in the context of global software development projects. An analytical framework is introduced for a better understanding of boundary spanners’ various roles in developing and maintaining trustful and sustainable client-vendor relations in complex, globally distributed projects. But first and foremost a model is developed that integrates trust development as a key boundary-spanning activity. With an outset in a model of boundary-spanning leadership it is shown how trust and trustworthiness has an impact throughout the boundary-spanning process. By emphasising that perceived trustworthiness and ultimately trust are important facets of boundary spanning, this chapter offers a contribution to boundary-spanning theory. First, by introducing the concept of trust-preparatory boundary-spanning activities; and second by discussing different modes of boundary spanning, and suggesting a distinction between the boundary spanner as a connector and as an intermediate.