Purpose: Mechanisms of Change (MoC) explain how strategies used to enhance the uptake of evidence in social and human services enable change in the behaviors of individual practitioners, organizational leaders or entire organizations, and systems. One such strategy is the use of implementation support practitioner (ISPs). This study examines the mechanisms through which ISPs facilitate behavior supportive of the implementation of research-supported interventions. Methods: A systematic, integrative review was conducted. The conceptualization of MoCs built on a model by Dalkin and colleagues. Results: Based on a unique combination of knowledge, skills, and attitudes, ISPs install trust in and among their stakeholders and utilize this trust to promote meaningful and relevant learning; provide ongoing opportunities for learning, reflection, and support; help to span boundaries; and positively motivate stakeholders. Discussion: ISPs do not represent a short cut to better implementation. They represent an additional implementation challenge that requires dedicated attention and resources.