This brief focuses on the importance of identifying, operationalizing, and implementing the “core components” of evidence-based and evidence-informed interventions that likely are critical to producing positive outcomes. The paper defines what is meant by “core component”, rationales for the importance of operationalizing core components, and explores implications for selecting, funding, implementing, scaling up, and evaluating programs. We will use the term core components to refer to the essential functions or principles that make up a program or complex intervention and the associated activities that operationalize each core component. Core components are directly related to a program’s theory of change, which proposes the mechanisms by which an intervention or program works. The core components are intended to, or have been demonstrated through research to, positively impact the proximal outcomes that address the identified needs and that increase the likelihood that longer-term outcomes will be achieved.