OBJECTIVES: Obesity has reached epidemic proportions and has many cost implications. Being overweight and obese is associated with higher rates of many chronic health conditions, which in turn leads to increases in medical spending and productivity losses. Many worksites have implemented weight management programs for employees to offset the cost burden of disease. This study modeled the potential cost savings for an employer from a 2-year worksite weight management program over ten year time horizon.   METHODS: We used data from a group randomized control trial of a worksite weight management program and published healthcare utilization data to model long term net costs. Using a Markov decision analytic modeling technique, we conducted a cost benefit analysis of weight management program versus usual practice. Program costs, health care utilization and prevalence of overweight and obesity in the study population were used to assess program impact. Sensitivity analyses were conducted to find a threshold at which the intervention would have a positive net benefit. RESULTS: The study population showed had a 1.44% decrease in the overweight/obesity in one year. When modeled over 10 years, this program incurred an excess cost of $206 per person compared to usual practice. The threshold at which this program would have a positive net benefit is when there is a 5.8% decrease in the overweight/obese population annually. CONCLUSIONS: Worksite weight management programs may yield cost savings with modest reduction in the percentage of overweight or obese employees.  This evidence may encourage employers to implement and support weight management programs that have empirically demonstrated higher rates of weight loss in employees. More research is needed to understand why some individuals are more successful at weight reduction and to evaluate long-term effectiveness of weight management at worksites.