Knowledge can be valorized in many different ways. University spin-offs have proven to be very effective as the knowledge generated in a university or research institute is directly translated into commercial activities. In addition, university spin-offs have played an important role in the economic and innovation growth of the region. While much effort has been taken to support the creation and survival of university spin-offs, there is still limited understanding regarding the factors that contribute to their growth. This study particularly intends to understand how university spin-offs use their networks in order to find resources needed for growth. By using a sample of spin-offs from two universities, TU Delft the Netherlands and NTNU Trondheim, Norway, a set of model is explored with a focus on characteristics of social networks through which knowledge is acquired, like tightness, strength, heterogeneity and spatial orientation. This is followed by an exploration on the role of social networks of university spin-offs in two different urban environment and development stages. The results indicate that loose networks, weak relationships and heterogeneous backgrounds of network partners enhance growth. In addition, this study found more differences than similarities in the social network profile and in its influence on growth, and in this sense a contrasting urban environment and development stage of spin-offs matters.