Green parties have been represented in the parliaments of European Union countries since 1981, but it was not until recently that a few have entered national governments. Using a data set comprised of 51 government formation opportunities (where the Greens were represented in parliament), the authors of this article show that the parties involved in these bargaining situations are more office-oriented than earlier studies had found. As Green parties are seen to be less office-seeking than other parties, this general tendency for office-seeking behaviour in government formation may partly account for the scarcity of Greens in government. Furthermore, a number of hypotheses derived from theories that account for the specific nature of Green parties in terms of their office-, policy- and vote-seeking orientations are tested. It is found that Greens participate in government when they have lost votes in at least one election, when the main party of the left identifies them as a clear electoral threat and when the policy distance between the Greens and either the formateur party or the main left party is small (the latter condition must be accompanied by a substantial proportion of seats for the Green party in parliament). As most of these simultaneous conditions only materialized recently, and in a few countries, it is argued that this analysis, which is the first comparative and multivariate test focused on this question, explains the scarcity and the delay of Green governmental participation.