The aim of this study was to examine the effect of 10 minutes of heart rate variability (HRV) biofeedback on cognitive performance and affect scores during induced stress. Eighteen healthy male volunteers (aged 23–41 years) exposed to work-related stress, were randomised into an HRV biofeedback intervention (BIO) and a comparative intervention group (COM). Subjects completed a modified Stroop task, which included having to mentally count 18 white squares randomly presented between colour words, before and after a 10-minute intervention. Subjects also completed questionnaires to rate their anxiety. BIO subjects improved their reaction times and consistency of responses, and made fewer mistakes in counting squares during the modified Stroop task. They also felt more relaxed, less anxious and less sleepy than the COM subjects. In conclusion our results suggest that short duration HRV biofeedback is associated with improved cognitive performance while concurrently aiding relaxation. Copyright © 2010 John Wiley & Sons, Ltd.