BackgroundThe benefits of physical activity (PA) have been well documented, and the worksite is a promising setting for PA promotion. The aims of this study were as follows: 1. To evaluate the effect of a group-based worksite intervention on PA and health-related outcomes by using pedometers. 2. To examine the associations between the change in vigorous physical activity (VPA)/moderate physical activity (MPA)/walking and health related outcomes.MethodsA total of 398 participants (221 in the intervention group (IG) and 177 in the control group (CG)) from 17 worksites were recruited for a prospective self-controlled trial of a worksite physical activity intervention program in China. In the IG, a pedometer was utilized to self-monitor the PA, together with group competition, goal setting, and other incentives. No intervention was applied to the CG. Physical activity, sedentary behavior, and health-related outcomes were measured at baseline and immediately after the 100-day period intervention.ResultsA total of 262 participants completed the program (68.3% adherence). Adherence in the intervention group was 67.9% (n = 150/221). Improvements between baseline and follow-up among intervention participants were observed in the following parameters: VPA (+ 109.7 METs/week; p < 0.05), walking (+ 209.2 METs/week; p < 0.01), systolic blood pressure (SBP; − 2.1 mmHg; p < 0.01), waist circumference (WC; − 2.3 cm; p < 0.01), body fat percentage (BF); − 1.0%; p < 0.01), and body mass index (BMI; − 0.5 kg/m2; p < 0.01). VPA was related to changes in body fat percentage (p < 0.05) and body mass index (p < 0.05).ConclusionThis integrated group-based intervention program contributed to comprehensive improvement in health-related outcomes. The study was useful for establishing associations between change in VPA/MPA/walking and health-related outcomes in a natural setting. Long-term evaluation is required to examine the potential of such an integrated intervention to promote PA.RegistrationThis study was prospectively registered in the Chinese Clinical Trial Registry. Trial registration number: ChiCTR-1,800,015,529. Date of registration: April 5, 2018.