This study examined teachers’ preparation as determinants of students’ performance in Mathematics. The study employed a descriptive research of survey type and quasi-experimental of pre-test, post-test control group design. The population comprises of all Junior Secondary School 2 students and their Mathematics teachers in Ekiti- State. The sample for the study consisted of 48 Mathematics teachers and 120 Junior Secondary School 2 students selected from all the 16 Local Government Areas of Ekiti- State using multistage and purposive sampling techniques. The instruments used for the study were Mathematics Teacher Questionnaire (MTQ) and Mathematics Student Performance Test (MSPT). The Hypotheses generated were tested using Analysis of Variance (ANOVA) at 0.05 level of significance. The findings revealed that teachers’ experience had significant influence on students’ performance in mathematics. The study also revealed that teachers’ qualifications had significant influence on students’ performance in Mathematics. Based on the findings of the study, it was recommended that governments and stakeholders in education should encourage experienced teachers to teach at the junior level of schools so as to lay good foundations for the students. Schools should also be staffed with highly qualified Mathematics teachers that can handle the job effectively.