In this paper we show that heart-rate based audio/sonification biofeedback (HRSB) can be used to facilitate emotion regulation during poker play. We report on a laboratory experiment (N= 29) where participants play No Limit Texas Hold'em poker while hearing heartbeats synchronized with their actual heart-rate (biofeedback condition) or at steady pace (control condition). The synchronized heart-rate biofeedback decreased emotional reactivity in terms of arousal (as measured by skin conductance) and valence (as measured by facial electromyography). We also observed individual differences between participants in the effectiveness of the HRSB. The participants were profiled using the behavioural inhibition/activation system (BIS/BAS) questionnaires, and there was a significant correlation between the effectiveness of the biofeedback method and BIS/BAS scores; with biofeedback being effective primarily for participants with high BIS/BAS scores.