The research, informed by the knowledge based view of the firm, explores the relation between pre-acquisition alliances between acquirer and target and post-acquisition innovation performance. Pre-acquisition alliances are a rare event and the work draws on an original dataset, incorporating financial, mergers and acquisitions, patents, and business news databases. The sample consists of 269 high technology M&As with pre-acquisition alliances, which is then compared with a matched sample of acquisitions without prior alliances. The research adopts 'doubly robust' matching and average treatment effect models to observe the causal effect of acquisitions with pre-acquisition alliances on innovation performance. The results show that acquisitions following pre-acquisition alliance between acquirer and target differ substantially from the pool of acquisitions without any pre-acquisition alliances. Further, the study looks into the variety of knowledge motivations in pre-acquisition alliances, such as: alliances motivated by exploration and exploitation with different levels of intensity. The result reveals that a distinction between the intensity of exploration and exploitation better explains the result. The study also focuses on knowledge relatedness (in particular, technology similarity and complementarity) between firms involved in acquisitions both with and without pre-acquisition alliances and the role it plays in post-acquisition innovation performance. The result shows that the presence of technology similarity in firms involved in acquisitions with pre-acquisition alliances makes the integration process smoother and more efficient. Therefore, the performance outcome can be observed more rapidly in such cases than that of acquisitions without pre-acquisition alliances. Conversely, in cases with technology complementary between firms engaged in acquisitions with pre-acquisition alliances, we observe less negative impact on post-acquisition innovation performance. This research contributes towards bringing strategic management and the knowledge based view of the firm closer together by focusing on the role of knowledge as motivation for acquisition in pre-acquisition alliances. The results illustrate a better understanding of the relation and effectiveness of pre-acquisition alliances and innovation performance, and a clearer operationalisation of concepts of post-acquisition innovation performance. The study findings suggest that managers developing both acquisitions and alliances, should also consider pre-acquisition alliances, and bear in mind the different nature and levels of intensity in knowledge motivations and knowledge relatedness between acquirer and target as a factor influencing innovation performance.