Using comparative data from a peer group of international and private financial institutions, this chapter explores what drives effectiveness in International Financial Institution (ifi) boards. It starts by identifying their overarching constituency nature and the dual role of directors as representative of shareholder governments and “fiduciaries” of the institution. It also underlines their somewhat contradictory power structure, with a high concentration of decision-making at board level, performed by non-professionals, whose nomination as “executives” belies the absence of any personal executive responsibilities in the organization even when these directors are full-time “residents”—another particularity of ifi boards. The main argument of the chapter is that, while these particularities are important, ifi boards resemble all other boards, especially those of private financial institutions, when it comes to the key drivers of their performance. These consists of their size, composition, leadership, diversity; the competencies and tenure of their directors; the quality of the support they get from management and the tools they use to maintain their effectiveness over time. The chapter concludes with some preliminary ideas on improving ifi board effectiveness.