This study examined the degree to which Teacher’s Self-efficacy determined students’ interest and academic achievement in Mathematics. The study adopted correlational research design. The study was guided by two (2) research question and two (2) hypotheses. The population of the study consist of 8 Mathematics Teachers and 5125 Senior Secondary II (SS2) students. A sample of 29 mathematics teachers and 400 students was used for the study. Four instruments were employed for data collection in this study. They are Teachers’ Self-efficacy scale (TSS), Students Mathematics Interest Scale (SMIS) which was developed by researcher and students’ Mathematics Achievement Pro-forma (SMAP). Face validity as well as construct validity were used to the instruments. The reliability indices of the Students Mathematics Interest Scale (SMIS) and Teachers Self-efficacy scale (TSS) were computed using Cronbach's Alpha (α). Regression analysis was performed to analyse the data, and regression ANOVA was utilised to test the hypotheses at the significance level of 0.05. The study's results, among other things, demonstrated that students’ interest in mathematics is determined by teachers self-efficacy (11.1%), found significant (p> 0. 05) determinant of students Interest in Mathematics, it also showed that students’ achievement in Mathematics is determined by teachers self-efficacy (11.2%), found to be significant determinants of students achievement in mathematics. Conclusion were drawn and implications of the findings of the study was highlighted. It was recommended that Teachers should strive to develop high self-efficacy, positive aversion and low anxiety towards the teaching of Mathematics in schools as to boost students’ interest and achievement in mathematics; Government agencies and school administrators should train in-service and pre- service teachers for self-efficacy to enhance students’ interest and academic achievement.