Heart Rate Variability (HRV) is increasingly relevant in applied psychology and medicine because it offers objective indices of autonomic flexibility tied to emotion regulation. Mindfulness interventions including brief, intensive, and online‐based programs have been studied in relation to HRV, using both time-domain (e.g. RMSSD, SDNN) and frequency-domain (e.g. high-frequency power, HF; LF/HF ratio) parameters. In this review (40 empirical studies from 2020–2025, randomized controlled trials, within-subject and longitudinal designs), we find that mindfulness significantly increases parasympathetic‐related HRV measures (notably RMSSD and HF) and reduces emotional distress (e.g. anxiety, stress) relative to baseline or control conditions. However, effect sizes are variable due to methodological inconsistencies (different HRV recording durations, resting vs. active tasks) and heterogeneous samples. The review highlights HRV’s promise as a biomarker for mindfulness‐based emotion regulation, especially when studies use standardized protocols. For maximum impact, future work should employ longer follow‐ups, rigorous RCTs, and integrate multi‐modal physiological and psychological measurement across diverse populations.