This study measured the correlation between mathematics self-concept and academic achievement of students at four schools in Vhembe District, South Africa. The study targeted Grade 12 candidates for the South African National Senior Certificate (matric). A sample of 236 respondents–112 boys and 124 girls–was selected from four schools using purposive and stratified random sampling. Two schools were in a rural area and two in an urban area. A questionnaire that included items from the Academic Self-Concept Questionnaire, and document analysis, were used to measure mathematics self-concept and academic achievement. Each respondent's mathematics achievement score was determined by averaging their mathematics scores over three consecutive terms. The multiple linear regression model and one-way analysis of variance (ANOVA) were used to test the hypotheses. The results of the study show that mathematics self-concept positively and significantly predicted academic achievement. Based on findings, the study makes recommendations for effective methods that teachers and other stakeholders can employ to increase students’ mathematics self-concept and boost students’ academic achievement.