The conferment of tenure at a United States university provides substantial job security to its recipients. Tenure is designed to allow a professor the ability to explore new and risky research questions without fear of losing their position due to lack of publications. At the same time, this policy creates an incentive system with an ambiguous effect on how the professor performs in the classroom. Professors may no longer care about teaching evaluations since future evaluations are unlikely to affect their job security. Alternatively, tenured professors, no longer having strenuous research priorities, may devote more resources to the teaching component of their job. This paper investigates the impact of the conferment of tenure on student evaluations of teaching. Data comes from a large, flagship state university and spans 22 semesters (2006-2017). We use an instructor-level fixed effects structure to compare end-of-semester course survey scores before and after an instructor receives tenure. We find that conditional on being granted tenure, professors experience a small, but persistent, decrease in student course evaluations. This effect is driven by professors in the top half of the course evaluation distribution.