This mixed methods study focused on the mathematical knowledge for teaching among primary mathematics teachers at an Oklahoma elementary school. A need for this study was determined by the lack of student achievement in primary mathematics at this elementary school. The study consisted of quantitative data collection in the form of two instruments. The instruments were designed to measure teachers' mathematical knowledge for teaching. Qualitative data were collected in the form of teacher interviews from four primary mathematics teachers. A mixed methods approach was used to gain a more complete picture of the experience and knowledge of primary teachers in mathematics. Findings reflected that teachers had a lower than average level of mathematical knowledge for teaching in the area of Numbers and Operations. They also reflected similar results in Patterns, Functions, and Algebra. Survey results detailed specific training and professional development teachers have received up to this point in mathematics, their teaching experience, and their interest in future mathematics professional development. This study was the first step in writing a recommendations report for the stakeholders of this elementary school. Stakeholders requested this information to design a plan for future professional development for its teachers. The goal of this professional development was to build on teachers' discovered weaknesses in primary mathematical knowledge for teaching in order to build their knowledge and affect student achievement in a positive way. [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/en-US/products/dissertations/individuals.shtml.]