Heart rate variability (HRV) has been receiving increasing attention not just in medical but also in psychological research. Several studies show that mental disorders are associated with lower levels of HRV. Therefore, HRV has been considered as a transdiagnostic biomarker. The current review spreads light on the possibility that in the connection of HRV and psychopathologies the deficits of emotion regulation or disregulated emotional states can be important mediators. Accordingly, we review the results of the questionnaire-based and experimental studies examining the connection of emotion regulation and resting and/or phasic HRV.