The workplace is a powerful setting to reach large numbers of at-risk adults with effective chronic disease prevention programs. Missed preventive care is a particular problem for workers with low income and no health insurance. The costs of chronic diseases among workers — including health care costs, productivity losses, and employee turnover — have prompted employers to seek health promotion interventions that are both effective and cost-effective. The workplace offers 4 avenues for delivering preventive interventions: health insurance, workplace policies, health promotion programs, and communications. For each of the avenues, the evidence base describes a number of preventive interventions that are applicable to the workplace. On the basis of the evidence and of our work in Washington State, we present a public health approach to preventing chronic diseases via the workplace. In addition to relying on the evidence, this approach makes a compelling business case for preventive interventions to employers.