This report presents the results of a systematic review of the effectiveness of worksite nutrition and physical activity programs to promote healthy weight among employees. These results form the basis for the recommendation by the Task Force on Community Preventive Services on the use of these interventions. Weight-related outcomes, including weight in pounds or kilograms, BMI, and percentage body fat were used to assess effectiveness of these programs. This review found that worksite nutrition and physical activity programs achieve modest improvements in employee weight status at the 6-12-month follow-up. A pooled effect estimate of -2.8 pounds (95% CI=-4.6, -1.0) was found based on nine RCTs, and a decrease in BMI of -0.5 (95% CI=-0.8, -0.2) was found based on six RCTs. The findings appear to be applicable to both male and female employees, across a range of worksite settings. Most of the studies combined informational and behavioral strategies to influence diet and physical activity; fewer studies modified the work environment (e.g., cafeteria, exercise facilities) to promote healthy choices. Information about other effects, barriers to implementation, cost and cost effectiveness of interventions, and research gaps are also presented in this article. The findings of this systematic review can help inform decisions of employers, planners, researchers, and other public health decision makers.