The study examined the relationship of study habits of students and their achievement in mathematics. The method used for the study was correlation design. A sample of 500 students were randomly selected from 25 public secondary schools in Delta Central Senatorial District, Delta State, Nigeria. Questionnaires were drawn to gather data on students' study habits. Students' results in mathematics were also collected from their various schools to gather data on their achievement in mathematics. Two research questions were formulated to guide the study. Regression and ANOVA were used to analyse the data. The following are the major findings: There was significant relationship between students' study habits and mathematics achievement. There was a significant difference in mathematics achievement between good study habits and poor study habits.