The purpose of this correlational study was to investigate the relationship of number sense comprehension and mathematics attitudes on mathematics achievement and intention to pursue a mathematics-related career for final-year high school students in Kenya. The sample for the study comprised of final-year high school students from three schools, including Wasamo Girls Secondary School, Sena Mixed Secondary School and Uozi Mixed Secondary School. Primary data for the study was collected through administration of a Number Sense Test and a two-part survey aimed at gathering data regarding students' attitudes and desire to pursue math-related career. Secondary data on math achievement was gathered through the average students' math scores attained for the last three academic years. Correlation, in addition to simple line regression and descriptive statistics, was used to analyze the collected data to establish and determine the relationship among the variables of interest. The results indicated that number sense had a positive and significant relationship on attitude towards mathematics and mathematics achievement. Additionally, the results illustrated a positive and significant relationship between attitudes towards mathematics and mathematics achievement. This implies that students' number sense and attitudes are positively correlated and, consequently, both are predictors of mathematics performance. However, despite the low performance exhibited by the students in this sample, a majority of them indicated a great desire to pursue math or STEM-related career, highlighting the need and a call for review of math career choices and their related prequalification standards, disciplines and subjects in general. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]