This paper explores ways that common evaluation approaches and practices constrain innovation and offer lessons about an emerging evaluation approach -- developmental evaluation -- which supports the adaptation that is so crucial to innovation. For what kinds of grantmaking strategies should funders consider using developmental evaluation? What organizational conditions are necessary for it to work? How can grantmakers grapple with the challenging questions that developmental evaluation raises about innovation, accountability, rigor, and adaptation? Drawing on the reflections and insights of foundation staff and evaluators who have experimented with developmental evaluation, it calls on philanthropy to re-envision the role, purpose, and processes of evaluation so that social innovations have a better chance of success. A short bibliography is included.