Workplace wellness programs have become increasingly common in the United States, although there is not yet consensus regarding the ability of such programs to improve employees’ health and reduce health care costs. In this paper, we study a program offered by a large U.S. employer that provides substantial financial incentives directly tied to employees’ health. The program has a high participation rate among eligible employees, around 80%, and we analyze the data on the first 4 years of the program, linked to health care claims. We document robust improvements in employee health and a correlation between certain health improvements and reductions in health care cost. Despite the latter association, we cannot find direct evidence causally linking program participation to reduced health care costs, although it seems plausible that such a relationship will arise over longer horizons.