The present study investigated the influence of extrovert personality trait on Mathematics achievement among secondary school students in Nyakach sub-county, Kenya. The study will be guided by Eysenck’s theory of Personality. The study employed the Concurrent triangulation design within the pragmatic of mixed method approach. The target population comprised of 20 Deputy Principals, 900 form three students, 20 Mathematics teachers and 20 H.O.D’s – Guidance & Counseling will be obtained. Data was collected through the Eysenck questionnaire, interview schedule, Standardized Mathematics exams for the schools and Mathematics document analysis. A pilot study was conducted to validate as appropriate the research instruments before the actual research commence. Content construct and face validity was ensured by use of research experts, while reliability will be ensured by split half method. Reliability test was above 0.5 implying high rate of reliability. Trustworthiness of qualitative instruments was ensured according to the four criteria. Quantitative data from the questionnaires was analyzed by both descriptive statistics and inferential statistics such a Pearson product correlation coefficient and regression analysis, while qualitative data was analyzed using thematic framework. There was a positive correlation (n=878; r =.353**; p <.01) between Being extrovert and Mathematic scores among students. Its recommended that teachers should purpose to blend this personality with others during group activities.