The purpose of this study was to examine mathematic academic achievement of 4th and 8th grade African American, Latinx, and Asian students by gender and content domains of TIMSS 2015 mathematics assessment.Major research findings for this study were: (1) Asianstudents reported higher mean scoresacross all content domains on both fourth and eighth grade TIMSS mathematics tests. (2) When it comes to gender difference of the 4th graders, the mean scores of African, Latinx, and Asian American boys were higher than their counterparts. However, on 8th grade tests,African American girls reported higher mean scoresthan African American boyson Geometry, Data & Chance, and Algebra. Moreover, 8th grade Latinx American girls scored higher than Latinx boys on Algebra. Conclusion and recommendations based on the results were explained.