The prime ministership is the preeminent political post in parliamentary democracies. Yet few studies examine PM party choice, perhaps under the assumption that the choice is a simple function of party size. In this article, we argue that key strategic actors and the context in which government negotiations take place can play a critical role in PM party choice. We test our hypotheses using a mixed logit with random coefficients on an original data set comprising PM selection opportunities in 28 European countries. Our methodological approach allows us to incorporate qualitative concerns about heterogeneity and causal complexity into our analysis. Contrary to conventional wisdom, we find that the largest party is often disadvantaged when it comes to PM party choice, that some presidents play an influential role in choosing the PM, and that the value of being the incumbent depends on one’s performance in office and how the previous government ended.