The purpose of this phenomenological study was to explore the adult students' perceptions of Game-Based Learning's mitigation of math anxiety in a STEM math course at a mid-sized university in Southeast Texas. The participants in this study included 11 students who identified as adult learners with math anxiety taught by the researcher in a STEM math course. Structured interviews were conducted utilizing the math anxiety framework (Luttenberger et al., 2018) with a focus upon antecedent, interacting, and outcome variables. Overall, Game-Based Learning in a STEM math course lowered students' perceived math anxiety. Family pressures, cultural expectations, teachers' attitudes, self-regard, prior knowledge, and interests influenced math anxiety. Game-Based Learning mitigated anxiety through fun, low-stakes, collaborative, competitive activities. Colleges should consider professional development in implementing Game-Based Learning to mitigate math anxiety and increase achievement. Researchers should consider how mitigating math anxiety through Game-Based Learning may improve retention and self-concept in STEM programs. [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.]