Social innovation has gained prominence as a way to address social problems and needs. Evaluators and social innovators are conceptualizing and implementing evaluation approaches for social innovation contexts; however, no systematic effort has yet been made to explore and assess the overlap between evaluation and social innovation based on the empirical knowledge base. We address this gap, drawing on 28 empirical studies of evaluation in social innovation contexts to describe what evaluation practices look like, what drives those practices, and how they affect social innovations. Findings indicate most had developmental purposes, emphasized collaborative approaches, and used multiple methods. Prominent drivers were a complexity perspective, a learning-oriented focus, and the need for responsiveness. Reported influences on social innovations included advancing strategies, improving delivery, balancing aggregate and local information needs, and reducing risk. Conflict resolution, the quality of relationships, and availability of time and capacity mediated these influences. More peer-reviewed empirical studies and a broader range of study designs are needed, including research on how evaluations influence social innovation processes over time, phases, space and scale.