The Asian Infrastructure Investment Bank [AIIB] is the world’s newest multilateral development bank [MDB] and already one of Asia’s largest international organizations by membership. This paper will compare the institutional structure of the AIIB with that of the Asian Development Bank [ADB] to identify areas in which the AIIB has innovated as a matter of international institutional law. In reviewing the constituent documents, bylaws, and operational policies of the two banks, the paper will juxtapose the AIIB and ADB’s approaches to membership, project finance, voting, and governance. It will identify not only innovations, but also the likely implications, positive and negative, thereof. Finally, it will assess the degree to which these innovations may impact the AIIB’s ability to partner with existing MDBs. In particular, the AIIB’s approach to project finance and governance mark a significant break from the status quo, while in other areas it has remained conservative.