OBJECTIVE: The aim of this trial was to investigate the effectiveness of a worksite intervention using kettlebell training to improve musculoskeletal and cardiovascular health. METHODS: This single-blind randomized controlled trial involved 40 adults from occupations with a high prevalence of reported musculoskeletal pain symptoms (mean age 44 years, body mass index 23 kg/m, 85% women, with pain intensity of the neck/shoulders 3.5 and of the low back 2.8 on a scale of 0–10). A blinded assessor took measures at baseline and follow-up. Participants were randomly assigned to training – consisting of ballistic full-body kettlebell exercise 3 times per week for 8 weeks – or a control group. The main outcome measures were pain intensity of the neck/shoulders and low back, isometric muscle strength, and aerobic fitness. RESULTS: Compared with the control group, pain intensity of the neck/shoulders decreased 2.1 points [95% confidence interval (95% CI) -3.7– -0.4] and pain intensity of the low back decreased 1.4 points (95% CI -2.7– -0.02) in the training group. Compared with the control group, the training group increased muscle strength of the trunk extensors (P<0.001), but not of the trunk flexors and shoulders. Aerobic fitness remained unchanged. CONCLUSIONS: Worksite intervention using kettlebell training reduces pain in the neck/shoulders and low back and improves muscle strength of the low back among adults from occupations with a high prevalence of reported musculoskeletal pain symptoms. This type of training does not appear to improve aerobic fitness.