Anxiety is a common presenting concern for individuals at clinical high risk (CHR) for psychosis and one treatment that may be effective for anxiety is heart rate variability (HRV) biofeedback. The aim of this study was to test the efficacy of HRV biofeedback in reducing anxiety and distress in those at CHR. Twenty participants who met minimum scores for anxiety and distress completed four weeks of a HRV biofeedback intervention and received pre and post intervention assessments. There was a significant decrease in presentation of dysphoric mood and impaired ability to tolerate normal stressors. There was no change on self-report measures of anxiety and distress. Feedback and adherence were generally good. HRV biofeedback may be a feasible treatment option for individuals at CHR who have concerns with impaired stress tolerance and dysphoric mood. Future studies with a randomized controlled trial design will be necessary to further determine efficacy.