This survey study aims to find out the self-regulation of higher secondary students in relation to achievement in mathematics. A sample of 300 first year higher secondary students studying during the academic year 2018-19 was selected by using simple random sampling technique from Tirunelveli district, Tamil Nadu. Data were collected with the help of Self-Regulation Scale constructed by Saileela (2013). The five point Likert scale consisting of 42 (38 positive and 4 negative) items was designed to assess students' Self-Regulation in learning mathematics. The research tools were distributed to the students with proper instructions as to get the exact data for this study. For analyzing the data, percentile analysis, mean, standard deviation, t-test, F-test and Pearson's product moment correlation were employed and the analyzed data were interpreted accordingly. The finding shows that there is a positive relationship between self-regulation and achievement in mathematics of higher secondary students.