This master’s thesis was performed with the purpose of analysing the influence of knowledge sharing on the performance of strategic alliances. For responding to the research question, a deductive approach was chosen; first, a theoretical model, based on existing theories about knowledge sharing in strategic alliances, was developed, which was then transformed into hypotheses; this was followed by a survey among 50 manufacturing firms within the EU. The empirical data was thereafter analysed and the hypotheses were tested through a regression analysis. The study revealed several results: (a) it became apparent throughout the theoretical research, that knowledge sharing is not directly measurable, but had to be described by its composing aspects; (b) the results obtained through the regression analysis showed that (1) the trust among the alliance partners, (2) the degree to which the firms’ shared knowledge is explicit, and (3) the degree to which the contributed knowledge is related to the firm’s core knowledge, have a positive impact on the performance of an alliance.