Purpose: The effectiveness of the 14-component evidence-based whole-school reform Success for All (SfA) has been well established, but research on its implementation is limited although fidelity of implementation is vital for the effectiveness of such a program. This review sheds light on this issue. Design/Approach/Methods: A systematic literature review was conducted to acquire an overview of qualitative and quantitative aspects of SfA's implementation in primary schools as well as to identify stimulating and hindering factors when implementing SfA. Sixteen studies, conducted in the United States and the United Kingdom, were included in this review. Findings: Results indicate that 48% of schools implemented SfA at the minimal level, 45% at a more advanced level, and 7% at an insufficient level. Information on the implementation for each of the 14 components was rare. Most of the factors that affected implementation were hindering factors rather than stimulating ones. For successful implementation of this evidence-based program, the crucial factors appear to be leadership, fulfilling organizational conditions, staff development, and relentlessly implementing all 14 components together. Originality/Value: This review shows that for an evidence-based program to be effective, implementation fidelity is a very serious concern, which needs to be addressed systematically.