Objectives: The primary objective of this study was to examine the role of self-efficacy in mathematics and mathematical mindset in effort regulation in mathematics. Effort regulation was defined as 'management of effort in learning activities in the face of difficulties'. Design: A large-scale survey (N=1448) with four cohorts of students in years 7, 8, 9 and 11 (M age=14.0 years, SD=0.46) was conducted. Methods: 1448 participants, from two comprehensive schools in the UK, completed a pen and paper survey. Demographic characteristics, measures of prior attainment and cognitive ability were provided by the schools. Results: Findings from this study showed that mathematical mindset and self-efficacy in mathematics both positively predicted effort regulation in mathematics. Furthermore, it appears that the effect of mathematical mindset on effort regulation in mathematics was mediated through self-efficacy in mathematics. Conclusions: This study provides initial support for the relationship between mathematical mindset and effort regulation in mathematics as a key process, mediated by self-efficacy in mathematics. These results contribute to the current understanding of effort regulation in adolescents and are indicative of possible ways to enhance effort regulation in mathematics. Implications of the findings for future research are discussed.