Health risk appraisals (HRA) are a common type of workplace health promotion programme offered by American employers. In the United Kingdom, evidence of their effectiveness for promoting health behaviour change remains inconclusive. This randomized controlled trial examined the effects of two HRA interventions on lifestyle parameters, mental health and work ability in a UK context. A total of 180 employees were randomized into one of three groups: Group A (HRA augmented with health promotion and education activities), Group B (HRA only) and Group C (control, no intervention). After 12 months, changes in mean scoring in 10 lifestyle, mental health and work ability indices were compared, Groups A and B demonstrated non-significant improvements in 70% and 80%, respectively, compared with controls (40%). Odds ratios revealed that, compared with the control group, Group A was 29.2 (95% CI: 9.22-92.27) times more likely to report a perceived change in lifestyle behaviour; Group B 4.4 times (95% CI: 1.65-11.44). In conclusion, participation in the HRA was associated with a higher likelihood of perceived lifestyle behaviour change which was further increased in the augmented HRA group, thereby providing preliminary evidence that HRA and augmented HRA in particular may help UK employees make positive healthy lifestyle changes.