This study, conducted at California State University (CSU) in Southern California, focused on student engagement factors and academic performance of supplemental instruction (SI) students concurrently enrolled in a gateway mathematics course. The purpose of this quantitative correlational survey study was to investigate engagement factors employed by SI students enrolled in gateway mathematics courses; the researcher explored the relationships of the SI students' engagement factors to their gateway mathematics course grades. The participants completed a web-based survey in which they responded to items regarding their behaviors, thoughts, and feelings as experienced in the gateway mathematics course and the SI class sessions. The responses were scored within 4 engagement factor scales including skills engagement, emotional engagement, participation/interaction engagement, and performance engagement. The results of this study provided support for 2 alternative hypotheses: (a) there was a positive relationship between each of the 4 engagement factors and the gateway mathematics course grades of the participants, and (b) there was a positive relationship of the linear combination of the 4 engagement factors to the gateway mathematics course grades of the participants. The findings of this research study supported 3 conclusions: (a) engagement is a multidimensional construct, and the more students are engaged in their studies, the more likely they are to earn higher grades in a gateway mathematics course; (b) academic support and resources are essential for student learning; (c) college success, specifically, positive academic course performance, is a significant indicator of persistence toward college completion. Recommendations based on the findings and conclusions of this study include regular collaboration of efforts among all university stakeholders to provide a variety of student-centered venues for academic support and resources to engage students in developing self-efficacy for academic success in gateway mathematics courses. [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.]