China is playing an increasingly large role in the global arena and the relevance of understanding what drives their behaviour in international affairs is thus more important than ever. Earlier research points to how China upholds legitimacy thorugh socioeconomic performance and how this largely influences their behaviour and actions. With a basis in the theory of Performance Legitimacy, coupled with the Two-Level Games theory of the interconnectedness at the national and international arena, this study aims to explore this relationship in further detail. The purpose of this study is thus to examine how internal legitimacy and international behaviour has varied during the time period 1979–2018 and what impact internal legitimacy has on international actions. A quantitive analysis was conducted, using several socioeconomic factors as indicators of internal legitimacy and Chinas outward foreign direct investments as a variable measuring international behaviour. The analysis shows that when socioeconomic conditions within China deteriorate, they tend to pursue assertive foreign direct investment patterns. Furthermore, the effect of this is even more clear comparing the time period before and after the protests at Tianaman Square, pointing to a shift in the upholding of legitimacy and strengthening the argument for Performance Legitimacy.