This three-article dissertation examined the implementation and impact of corequisite mathematics courses at four North Carolina community colleges located in urban areas. The first article was a multiple case study that examined student and instructor experiences to determine the characteristics of corequisite courses that students and instructors found effective and their suggested changes to the corequisite course model to make it more effective. Overall, students and instructors found the corequisite course model effective and described the benefits of these courses, specifically the opportunity for just-in-time learning. The second article utilized a convergent parallel mixed methods design to explore the impact of corequisite courses. Findings indicated that characteristics of corequisite courses, specifically just-in-time instruction and the time spent in the course, positively influenced students' math self-efficacy and helped decrease their math anxiety. The increase in students' math self-efficacy was significant. The third article was a convergent parallel mixed methods design that examined the impact of corequisite instructors. Corequisite instructor's pedagogical decisions, personalities, classroom environment, and interactions with students were found to help students develop a growth mindset, decrease their math anxiety, and increase their math self-efficacy. An instructor's disposition, their approach to mistakes and questions, and their ability to create a safe and comfortable classroom environment were noted by students as being the largest influences on their mindset, math anxiety, and math self-efficacy. Community colleges and instructors should consider threats to just-in-time learning when designing corequisite courses, as well as, how instructors can positively influence students' experiences when taking a corequisite mathematics course. [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.]