The purpose of this study was to explore how evaluators justify using story-based methodologies when examining causality. The two primary research questions of the study included: 1) what arguments are made by evaluators to justify the credibility of story-based causal methodologies to evaluation stakeholders; and 2) from the perspective of evaluators, how do contextual factors influence whether story-based causal methodologies are perceived as credible by evaluation stakeholders? A case study was conducted to examine the cases of four evaluators who had experience implementing a story-based methodology in an evaluation. Data collection procedures included two interviews with each participant and a review of materials related to their story-based evaluations. Analysis of the data revealed cross-case themes highlighting participants' arguments for how they justify using story-based methodologies for causal examination. The first argument was that these methodologies can credibly be used to examine causality when the evidence needed aligns with the type of evidence produced by these methodologies. The second argument was that these methodologies can add credibility to a causal study because they reduce evaluator bias by elevating participant voice in the data collection process. The third argument was that participants can generally be trusted to provide true accounts; thus, their accounts of how change occurred for them are credible forms of evidence. And finally, the fourth argument was that these methodologies include procedures to triangulate participant accounts with other sources of data, thereby enhancing the credibility of the evidence produced. The study also included an examination of contextual factors that may contribute to these methodologies being perceived as credible by evaluation stakeholders. Findings revealed that stakeholders in the following contexts might be more likely to perceive story-based methodologies as credible: learning contexts, low-risk contexts, multi-cultural contexts, and contexts that value centering participant voice. As a contribution to the evaluation field, this study also provided a practitioner's guide for evaluators needing to justify using story-based methodologies for causal examination. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]