The study looks at the case of a university language center in Japan that administers a compulsory English language course. To provide some level of standardization for the course, and to better meet the educational aims of the center, a content and language integrated learning (CLIL) teaching approach has been set as center policy. The research examines the different conceptions of CLIL that exist among the multiple teachers of the course, how these conceptions were developed, and what implications this has for centers that administer similar courses. Data were collected through one-to-one interviews. A phenomenographic analysis of the data reveals categories of the different conceptions of CLIL and how those conceptions were developed. Activity theory, and consideration of the teaching of the course as an activity system, is employed to consider how the use of a teaching approach policy impacts teachers' engagement with working on the course. The study's findings indicate that teachers teaching the same course have different conceptions of the policy-directed teaching approach that they are asked to use. This is partly due to the various ways in which they develop their conception of that teaching approach. These differences are viewed as a contradiction typical of an activity system. A key implication of this contradiction is that it may lead to benefits such as promoting peer interaction and engagement with the course. The deployment of activity theory to consider use of a teaching approach policy within a university center is unique and results in implications for other such centers.