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Pulse rate variability (PRV) is often used as an alternative to heart rate variability (HRV) to measure psychophysiological function. However, its validity to do so is unclear, especially in adults with spinal cord injury (SCI). This study compared PRV and HRV in adults with higher‐level SCI (SCI‐H, n = 23), lower‐level SCI (SCI‐L, n = 22), and able‐bodied participants (AB n = 44), in a seated position as a function of performance in a reactivity task (Oxford Sleep Resistance Test: OSLER). PRV and HRV was measured using reflective finger‐based photoplethysmography (PPG) and electrocardiography, respectively, at baseline, immediately post‐OSLER, and after five‐minute recovery. Agreement between PRV and HRV was determined by Bland–Altman analysis and differences between PRV and HRV over time by linear mixed effects model (LMM) analysis. Concurrent validity was assessed through correlation analyses between PRV and HRV. Additional correlation analyses were performed with psychosocial factors. Results indicated insufficient to moderate agreement between PRV and HRV. LMM analyses indicated no differences over time for standard deviation of normal‐to‐normal intervals and low‐frequency power but significant differences for root mean square of successive differences and high frequency power. Nevertheless, PRV and HRV were highly correlated (Median r =.878 (.675–.990)) during all assessment periods suggesting sufficient concurrent validity. Similar correlation patterns were also found for PRV and HRV with psychosocial outcomes. While differences existed, results suggest PRV derived from reflective finger‐based PPG is a valid proxy of HRV in tracking psychophysiological function in adults with SCI and could therefore be used as a more accessible monitoring tool. Autonomic dysfunction is a serious problem following a spinal cord injury (SCI), but assessment remains a challenge. We present evidence showing pulse rate variability is a valid measure of autonomic activity in SCI and which arguably, is more accessible in clinical settings than the gold standard heart rate variability. [ABSTRACT FROM AUTHOR]