The importance of evaluation use has led to a large amount of theoretical and empirical study. Evaluation use, however, is still not well understood. There is a need to capture the complexity of this phenomenon across a diverse range of contexts. In response to such complexities, the notion of “evaluation influence” emerged. This article presents a theory of evaluation influence within public sector partnerships. An analysis of key concepts is used to develop propositions about the relationships between evaluation attributes, partnership functioning and characteristics, partnership evaluation behavior, individual characteristics, contextual factors, and evaluation influence. The model highlights the complexities of evaluation influence and identifies a range of factors that evaluators can consider in practice. The model also extends on existing theories of evaluation influence in considering the role of individual characteristics, stakeholder evaluation behavior, and partnership contexts.