This study explores the implementation of mandatory seasonal influenza vaccination policy for health care workers at BJC Healthcare, a large Midwestern health care organization of approximately 26,000 employees. The purpose of this study is to gain insight into the effectiveness and issues of mandatory seasonal influenza vaccination of health care workers. A single-case study approach is utilized, along with the systems theory as a theoretical framework. By examining the implementation of mandatory seasonal influenza vaccination policy at BJC Healthcare, this study is able to categorize three potential areas of conflict under the systems theory: technology, the labor force, and the task environment. Discussion of these three sources of uncertainty and conflict allows for greater understanding of the issues of implementing mandatory seasonal influenza vaccination policy that need to be resolved in order to promote health care institution effectiveness, function, and successful implementation of mandatory seasonal influenza vaccination policy.