The purpose of this study was to determine if there was a relationship between teacher mathematical knowledge (content and pedagogy) and the mathematics achievement of students in grades four and five. This study used a quantitative approach using Hierarchical Linear Modeling (HLM). Through a quantitative study based upon a teacher assessment of mathematics content and pedagogy and a student assessment entitled the Measures of Academic Progress (MAP), the researcher measured the teachers' mathematical content knowledge, mathematical pedagogy knowledge, and analyzed the data to determine if there was a relationship between teacher knowledge and student achievement. The assessments were based on the Maryland state curricular standards. All teachers involved in the study were considered generalists at the elementary level. Student achievement was measured through MAP. Through the use of the teacher knowledge assessment, the study provided valuable data that could be used to inform colleges providing training to pre-service teachers, principals, supervisors, and those providing professional development to elementary teachers. Additionally, the study could be used to inform teacher education and education policy efforts intended to strengthen and support teacher quality while improving the achievement of students in mathematics.