In response to decreasing motivation in high school math classrooms, teachers are transforming classrooms with various instructional techniques. Traditional math instruction relies on direct instruction and memorization of content, processes, and skills. Teachers are transitioning to more constructivist student-led approaches. Utilizing multiple instructional designs provides teachers more opportunities to access the major components of the ARCS Model: attention, relevance, confidence, and satisfaction. Therefore, the purpose of this action research was examining problem-based learning in a flipped classroom instructional environment and measuring its effect on students' motivation and achievement in Algebra 2. The study addressed the following research questions: (1) What is the impact of problem-based learning in a flipped classroom instructional environment on students' motivation in mathematics?; (2) What is the impact of problem-based learning in a flipped classroom instructional environment on students' self-efficacy in mathematics?; (3) What is the impact of problem-based learning in a flipped classroom instructional environment on students' mathematics achievement on Systems of Equations and Quadratic Functions?; and (4) What are students' perceptions of problem-based learning in a flipped classroom instructional environment? The action research innovation lasted seven weeks. Students responded to a Motivation in Mathematics Survey and answered items from a Diagnostic Test on Systems of Equations and Quadratic Functions, before and after the innovation period. Students' diagnostic test scores showed a significant increase (t(21) = 4.75, p < 0.001, Cohen's d = 1.01) from preinnovation to postinnovation measures. However, students' overall motivation (t(21) = 0.91, p = 0.187) and self-efficacy subscale scores (t(21) = 1.69, p = 0.053) on the motivation survey were not significantly different. Students also participated in interviews and math journals, in conjunction with teacher observations. Findings were analyzed to establish five themes: (1) Students desired more traditional structure than problem-based learning in a flipped classroom; (2) Problem-based learning was time consuming and prevented practicing math skills; (3) The encouragement and effort of their teacher positively affected their motivation more than other factors; (4) Motivation was lower due to time required and time of the school year; and (5) Students developed real-world skills through engaging, relevant, and high value tasks. [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.]