This quantitative study examined if external and internal factors predict elementary instructional coaches of mathematics beliefs about their mathematics coaching effectiveness in urban school settings. Internal factors were within the instructional coaches’ control, such as years of coaching experience and educational level; external factors were outside of their control, specifically school and district policies and practices, including the number of teachers served, the number of subjects coached, and the amount of time allotted with teachers. Participants in this study were 51 full-time elementary instructional coaches who supported mathematics in a large, urban school system in the Southeastern United States. Data collection was via the Coaching Skills Inventory, which includes 20 items focused on mathematics coaches’ self-efficacy related to their professional responsibilities, such as building teacher relationships, coaching skills, and knowledge of mathematical content and pedagogy. Additional data collection was via demographic and informational items that provided insights into various external and internal factors. Multiple regression methods were the statistical approaches used for analysis to determine if internal and external factors have an aggregate influence on mathematics coaching self-efficacy. The collective results of the regression model were not statistically significant, indicating that there is not a strong predictive relationship between internal factors, external factors, and aspects of mathematics coaching self-efficacy. However, the analysis showed that elementary instructional coaches of mathematics had relatively high self-efficacy related to student-centered pedagogy. Participants ranked the amount of time available to spend with teachers and the number of years of experience teaching elementary mathematics as the most important factors for their mathematics coaching effectiveness. The findings indicate potential factors that could help school and district leaders make decisions about the selection, support, and work setting of mathematics coaches.