The involvement of firms in innovation cooperation with different partners has become a widespread phenomenon in the contemporary business landscape. Our paper provides a review of extant alliance, innovation, open innovation and inter-firm collaboration literature and organizes it based on a conceptual framework featuring three levels of analysis: (a) the dyadic level, (b) the network level, and (c) the location level. The article identifies roadmaps in each of these areas and also highlights existing gaps in the present understanding of innovation cooperation. Thereby, it outlines a research agenda by identifying key research questions and issues in the areas where further research is needed and encouraged.Sustainability 2018, 10, 4517 3 of 32 changes that create the economic space of a given country [29] In this space, which Freeman called the National Innovation System, there are more or less formalized networks of cooperating companies and institutions. Indeed, as Fomina et al. [30] argue, the stability of economic development is determined by the features of the network structure in a collaborative engagement of enterprises. Therefore, it is legitimate to explore whether and how the location of companies and other institutions influence their cooperation for the development of innovation, and the performance outcomes thereof.Economic geography has developed the concept of proximity to explain the formation of networks and clusters of innovative companies in industrial districts [31,32]. The different dimensions of proximity may explain some of the positive externalities, such as knowledge creation and transfer, as well as innovation, which are generated by companies that are co-located [33]. According to Boschma [34], proximity implies similarity between actors and organizations, including both a geographical or spatial dimension and other non-spatial dimensions. Knoben and Oerlemans [35] note that "the concept of proximity has been used in many different ways in the literature, this including different measures and definitions".Boschma [34] identifies five types of proximity: