Evolutionary Evaluation, Relational Developmental Systems Theory, and Systems Thinking are three broad foundational theoretical perspectives that characterize the shifting paradigm in contemporary evaluation. They are central to the development of Relational Systems Evaluation (RSE). From Evolutionary Evaluation, we focus on the variation and selection role of evaluation, as well as the notions of ontogeny, phylogeny, symbiosis, and co-evolution. From Relational Developmental Systems Theory, we highlight how mutually beneficial bidirectional relations between a program and its environmental context can promote adaptive regulations. From Systems Thinking, we emphasize part–whole relationships, static and dynamic processes, the related concepts of scale and boundaries, multiple perspectives, and causal pathways. We propose that these theoretical elements—all of which are operationalized through RSE—can be transformative in our thinking about the next evolutionary stage for evaluation.