The purpose of this study was to examine the effects of a heart rate variability biofeedback (HRV BFB) intervention on pain catastrophizing and the psychological response variables of injured athletes. HRV BFB effects on athletes' physiological indices including heart rate variability (HRV), heart rate, and respiration were also assessed. Participants were 28 athletes who had sustained a moderate to severe musculoskeletal sports injury, ranging in age from 18 to 36 years (Mage = 20.82, SD = 3.41). All participants were out of training and competition and engaged in a rehabilitation program. This investigation was experimental in nature with a randomized, single-blinded study design. Participants were randomized into one of three conditions: HRV BFB intervention, HRV BFB placebo, or control conditions. Assessments of psychological outcomes and physiological indices were assessed at Baseline, Week 1, Week 2, and Week 3. Compared to placebo or control groups, athletes who received the HRV BFB intervention reported significantly greater reductions in devastation (F(6, 75) = 5.84, p < .001, η2 = .32), isolation (F(5.53, 69.07) = 2.69, p = .024, η2 = .18), pain magnification, and resting respiration rate (F(6, 72) = 7.37, p < .001, η2 = .38); these athletes also reported significantly greater improvements in reorganization (F(6, 75) = 2.73, p = .019, η2 = .18) and low-frequency HRV (F(6, 72) = 2.72, p = .019, η2 = .19). The findings suggest that HRV BFB may hold potential to improve athletes' psychological responses and pain magnification after sustaining an injury and that it shows promise as a useful psychological intervention for injury rehabilitation.