The Common Core Math Standards are more rigorous than previous state standards and represent a large shift in both content and pedagogy across the grade levels. With the pressure on principals to implement the more rigorous Common Core Math Standards and to ultimately raise student achievement, it is important to look at the role of the principal as instructional leader in facilitating standards implementation. This quantitative study explored the leadership actions of middle level principals in implementing the Common Core Math Standards and how those actions related to improvement in math instruction and student achievement as measured by the change in the percentage of students scoring at or above proficiency for the building on the New York State Common Core Mathematics Tests from 2013 to 2015. The researcher used an electronic survey to ask middle level principals across New York State, with the exclusion of non-public schools and schools in the five large city districts, about their actions to support the implementation of the Common Core Math Standards, to assess and respond to their teachers’ implementation of the Common Core Math Standards, and to support the ongoing growth of their math teachers in general. From the responses, middle level principals demonstrated a trend for a deeper level of involvement with actions that required a more organizational or managerial leadership role than with actions that required the principal to act in more of an instructional leadership capacity. This study also found a statistically significant positive correlation between the actions middle level principals utilized to support their staff in the implementation of the Common Core Math Standards and student achievement. From the results of this study, the researcher recommends more comprehensive structures and supports to help increase the capacity of principals and districts to be able to navigate this significant shift in instruction required by the Common Core Math Standards. Skilled leadership is an important part of guiding staff learning and improving instruction and as Cotton (2003) found, “studies have shown that principals who are knowledgeable about and actively involved with their school’s instructional program have higher-achieving students than principals who manage only the non-instructional aspects of their schools” (p. 25).