Purpose: The aim of this study was to compare the effects of low ([LV]; 4 total sets), moderate ([MV]; 8 total sets), and high set volumes ([HV]; 12 total sets) in acute full-body resistance exercise sessions on post-exercise parasympathetic reactivation measured using RMSSD. Methods: Ten resistance-trained participants (25.8 +/- 6.8 yr., 173.4 +/- 10.6 cm, 75.4 +/- 9.9 kg) performed three resistance exercise sessions. During each session, heart rate variability (HRV) was measured pre- and for 30 min post-exercise, divided into 5-min segments stabilization, Post(5-10), Post(10-15), Post(15-20), Post(20-25), and Post(25-30). Repeated-measures ANOVA was used to assess differences within and between pre-post exercise natural logarithm RMSSD (LnRMSSD) values. To assess the initial change in LnRMSSD, the delta percent change (DeltaLnRMSSD) from pre-exercise to Post(5-10) (DeltaLnRMSSD(pre-post)) was calculated for each session. The DeltaLnRMSSD was also calculated between Post(5-10) and Post(25-30) (DeltaLnRMSSD(post5-30)) to assess recovery. Results: Significant differences were observed between sessions and when comparing pre-exercise values to all post-exercise times across sessions (p </= .05). The LV session resulted in significantly higher mean LnRMSSD value (3.62) post-exercise compared to both the MV (3.11, effect size [ES] = 3.77) and HV (3.02, ES = 3.92) sessions while the MV and HV sessions produced similar responses. Across sessions no return to baseline occurred and when comparing sessions, no significant differences were found in DeltaLnRMSSD(pre-post) or DeltaLnRMSSD(post5-30). Conclusion: Acute bouts of full-body resistance exercise can cause similar reductions in LnRMSSD from pre-exercise levels and can delay parasympathetic reactivation back to baseline values during the same 30-min recovery period despite differences in set volume.