Chronic health conditions and multiple health risk factors afflict Americans and burden employers, but effective, affordable, workplace-based health promotion interventions have not been widely implemented. This is the first study to adapt the empirically validated Chronic Disease Self-Management Program for a general employee population in a workplace setting with an emphasis on disease prevention and health promotion. A quasi-experimental, wellness standard of care comparison, prospective cohort design was used among employee participants at a large University employer. Ninety-one individuals participated in the program. Participants reported significantly increased health behavior frequency and self-efficacy after the intervention, compared with their pre-intervention scores, and improvements were sustained at 3-month follow-up [self-rated abilities for health practices scale (SRA): F = 30.89, P < 0.001; health promoting lifestyle profile-II (HPLP-II): F = 36.30 P < 0.001]. Individuals in the intervention group reported improved self-efficacy and health behaviors compared with the wellness standard of care comparison group at post intervention (SRA: F = 12.45, P < 0.001; HPLP-II: F = 25.28, P < 0.001). Adapting lay-facilitated self-management for the workplace offers promise as a replicable, scalable, affordable model for culture change in organizations.