The multilateral development bank (MDB) model is a powerful multiplier of shareholder capital in support of development. But much more is expected of MDBs in the 21st century given the magnitude and urgency of development and climate challenges confronting the globe. This paper assesses the performance of the model against borrowing and non-borrowing shareholder priorities and expectations, and asks: what would an ideal development and climate bank look like? The analysis assesses MDB performance across four dimensions to define how the current model should evolve: the financial model, finance instruments for governments, finance instruments for the private sector, and impact measurement and reporting