Mathematics is an important component of our everyday lives. It involves necessary skills, such as computation, problem solving, and critical thinking. In spite of this, a significant portion of our students are unable to demonstrate proficiency. These students are typically the underserved, marginalized students who are over represented in remedial classes and behavioral statistics (Gibson, 2022; Harper, 2010, 2021; Zilanawala, et al., 2018). This research study presented two instructional interventions, culturally relevant pedagogy and problem-based learning, to examine the impact of self-efficacy, critical thinking, and mathematical achievement. This study utilized a mixed-methods triangulation design. The participants of this study were 36 third-grade students, who were assigned to this researcher's homeroom and targets math classes. Data collection instruments included pre- and post- student surveys, behavioral checklists, and semi-structured student interviews. Results of this study indicated that culturally relevant pedagogy and problem-based learning had a statistically significant impact on student attitudes, critical thinking skills, and mathematical achievement. [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.]