Firms increasingly engage in multiple strategic alliances simultaneously, often with partners from different industrial and national backgrounds. This results in portfolios of alliances that increasingly become larger and more complex. At the same time, firms realize different performance outcomes from their alliance portfolios; however, it is unclear why this is the case. Extant theories only provide partial insight into the underlying reasons for this inter-firm performance heterogeneity. This paper provides a critical assessment of traditional theorizing in alliance research, with a view to how they have informed motives for alliance portfolio formation but have also (partly) fallen short of explaining the performance heterogeneity among firms’ alliance portfolios.

Keywords:: alliance portfolio, alliance portfolio formation, alliance portfolio success, dynamic capability view, social network theory, resource-based theory, theory review, alliance capability