The Pacific Journal of Science and Technology –140– http://www.akamaiuniversity.us/PJST.htm Volume 17. Number 1. May 2016 (Spring) Effectiveness of Motivational Enhancement Therapy in Enhancing Mathematics Learning Gains among School-Going Adolescents in Oyo State, Nigeria. Adebayo David Oluwole, Ph.D. and Muraina Kamilu Olanrewaju Department of Guidance and Counselling, Faculty of Education, University of Ibadan, Ibadan, Nigeria. E-mail: muraina_kamilu@yahoo.com ABSTRACT The purpose of this study was to examine the effectiveness of motivational enhancement therapy in enhancing mathematics learning gains among school-going adolescents in Oyo State, Nigeria. Pretest-posttest, control group quasi- experimental design with a 2X2 factorial matrix was used in the study. The simple random sampling technique was used in selecting sixty (60) participants from two (2) local government areas in Oyo State, Nigeria. The respondents were measured with relevant adopted standardized scales (instruments) and the data obtained was analyzed using Analysis of Covariance (ANCOVA) statistical analysis. Three research hypotheses were formulated and tested at 0.05 level of significance. The result showed that there was significant main effect of treatment on students’ mathematics learning gains (F (2, 47) = 82.224, p < .05, = .681), there was no significant main effect of gender on students’ mathematics learning gains (F (1, 47) = .133, p > .05, = .002) and there was no significant interaction effect of treatment and gender on students’ mathematics learning gains (F (2, 47) = .044, p > .05, = .001). In view of these findings, the study stressed that the students should be trained on the effective usage of this interventions (motivational enhancement therapy), Experts in educational testing/evaluation and Counseling/Educational psychologists should intensify their effort to organize seminars/conferences on the implications of this intervention and moderating variables (that is gender among others) as they interact with students’ mathematics learning gains in the school. (Keywords: motivational enhancement therapy, mathematics learning gains, school-going adolescents) INTRODUCTION Mathematics is one of the compulsory subjects that students must complete in Junior Secondary School (JSS), regardless of whether such students intend to be in science, commercial, arts or social science in Senior Secondary School (SSS) class. In secondary school curriculum according to National Policy on Education (2004), mathematics is one of the core subjects that for the students to further their studies in Senior Secondary School (SSS) or institutions of higher learning especially in University, students are expected to have credit in it. This makes mathematics one of the essential subjects for students’ advancement. Mathematics is one of the subjects that is taken very seriously in the school system, irrespective of country or level of education. It has been described as a model of thinking which encourages learners to observe, reflect and reason logically about a problem and in communicating ideas, making it the central intellectual discipline and a vital tool in science, commerce and technology. In the words of Salman (2005), mathematics is a precursor of scientific discoveries and inventions. It is the foundation for any meaningful scientific endeavor and any nation that must develop in science and technology must have a strong mathematical foundation for its youths. In terms of curriculum relevance, mathematics is compulsory at the secondary school level and a prerequisite for moving from the Junior Secondary School (JSS) to the Senior Secondary School (SSS); just as at the tertiary level of education, a sound background in mathematics is a necessary condition for the study of all science, technology and social science based courses, as required by the Unified Tertiary and Matriculation Examination (UTME).