Program evaluation aims at establishing the quality of a program in order to generate a judgment that is valid and credible for the stakeholders. The present research aimed to gain a better understanding of the term "credible judgment" and to identify the required conditions to generate it. Semi-structured interviews were conducted with six experienced evaluators and clients. The results highlight the required conditions to ensure credible judgment: rigorous methodology, quality information, representation of various viewpoints, and coherence in developing argumentation. The contribution of this study consists in validating the thinking of particular theorists, while pointing out the pitfalls that arise in the transition from theory to professional practice.