In this paper, I explore theoretically the issues of meta-organizations' diversity and agency through a cross-literature analysis, thereby establishing a bridge between two strands of literature that until now have strikingly developed in total isolation. I show that one of the most distinctive traits of global union federations relates to their meta-organizational activities that take place at the firm level and reflect a complex, multi-level meta-organizational configuration where the upper level interacts directly with second-order members but the intrinsic exteriority of global union federations to the corporate unions network positions them as "meta-organizational network brokers". I also elicit two main dimensions of differentiation among meta-organizations that have been only indirectly delineated in the literature and which could constitute useful analytical tools for characterizing meta-organizations from a comparative perspective: (1) the degree of consistency between the goals of meta-organization secretariats and the objectives pursued by meta-organization members; and (2) the degree and direction of asymmetrical interdependence between the meta-organization itself and its members. I argue that both dimensions strongly condition the capacity for agency of their secretariat, and ultimately the degree of actorhood and the capacity of meta-organizations to act as autonomous and influential organizational actors.