Working as One World Bank Group iscentral to the WBG’s strategy of helping countries endextreme poverty and promote shared prosperity sustainably.Over the past 20 years (1995 to 2015), many initiatives havesought to boost WBG effectiveness by increasing the numberof projects jointly financed by IFC, MIGA, and/or the WorldBank.Yet the number of joint projects still amounts to avery modest share of the overall WBG project commitments.This first systematic stocktaking by IEG of joint orco-financed projects within the WBG offers insight on bothbenefits of, and challenges in, developing, structuring,supervising, monitoring and evaluating joint projects.Itdraws lessons from past experience, staff and clientfeedback, and highlights implications for WBG managementregarding expectations of increased co-financed projects inthe future.