This study developed an instrument that measures the attitude of Filipino high school students towards mathematics, with reliable predictors and factors. Using the responses of 300 high school students from Zamboanga Sibugay, the validity and reliability of the Mathematics Attitude Scale (MAS) was tested using Exploratory Factor Analysis (EFA) and reliability analyses. The EFA showed that four-factor structures of the instrument, regarding the mathematics attitude for high school students, explained 27.48% of the variance in the pattern of relationships among the items. The Average Variance Extracted (AVE), Composite Reliability, and Cronbach’s Alpha coefficients were reported. They proved that the extracted constructs have obtained and satisfied convergent validity. Thirty-three items remained in the final questionnaire after deleting the twenty-seven items with factor loadings of less than 0.4 (Students’ Perceived Motivation and Support in Learning Mathematics: twelve items; Students’ Perceived Anxiety in Learning Mathematics: ten items; Students’ Perceived Self-Efficacy in Learning Mathematics: six items; and Teachers and Parents’ Influences to Students in Learning Mathematics: five items). This study has confirmed the four-factor structure of the MAS. Educators and researchers can use the MAS to better understand the attitudes of Filipino high school students towards mathematics.