Integrating theoretical perspectives is very useful when we investigate an empirical phenomenon, and this article demonstrates how employee motivation can be understood based on principal-agent, self-determination, and prosocial theories. Employee motivation can be conceptualized as either extrinsic, autonomous or prosocial or a combination thereof, and a theoretical synthesis allows us to understand this complexity without losing too much coherence and parsimony. We illustrate the theoretical integration specifically for public sector outsourcing and digitalization. Although these empirical settings are relevant in themselves, they serve primarily as grist for a wider discussion on strategies for applying multiple theoretical perspectives and crafting a synthesis. The key contribution of the article is thus theoretical - to develop a coherent understanding of employee motivation - but the empirical illustrations also give insight into the motivation of employees in the context of public sector outsourcing.