This study examined the impact of a worksite health promotion program on short-term disability (STD) days in a large telecommunications company. The evaluation used a quasi-experimental, multiple time-series design with between-group comparison of workdays lost due to STD to determine impact. The study period was 3 years and included 1628 employees on STD leave. Self-selected program participants were compared with non-participants on net days lost at three assessment points: the year before the launch of the program, and each of 2 years post-launch. A comprehensive health promotion program was developed to reduce health care costs, improve employee satisfaction, and enhance the employer’s image. Key features of the program included reimbursement for employees participating in the Health Risk Assessment and in wellness or fitness activities. Other features included occupational health services, targeted interventions for high-risk employees, self-care materials, and a nurse advice line. Results revealed no significant differences at baseline between participants and non-participants for net days lost while on STD leave. At the post-program launch, non-participants’ net days lost significantly increased from 33.2 to 38.1 when controlled for age, gender, job type, tenure, and STD category, whereas the participant group average net days lost decreased from 29.2 to 27.8. After adjusting for baseline differences, we found a 6-day difference between groups, which represented a 20% program impact. This study found that participation in a health promotion reimbursement program had a significant impact on average net days lost for employee STD absence. These findings represented potential savings in excess of $1,371,600 over a 2-year period. Future program evaluation efforts will address the impact on medical care costs related to program participation.