Objective: The aim of the present study was to study time indices of heart rate variability (HRV) in patients with mitral annular calcification (MAC). Materials and Methods: A cross-sectional observational study was performed. Fifty patients with echocardiographic evidence of MAC and 50 age- and gender- matched control subjects without echocardiographic evidence of MAC were included. All the study participants underwent 2-dimensional echocardiographic examinations and 24-hour Holter monitoring for HRV analysis. Student-t, Mann-Whitney U and Chi-square tests were used for statistical analysis. Results: Hypertension and coronary artery disease were more common in the MAC group than in the control group. All HRV parameters including mean RR interval, SDNN, SDANN, SDNN index, pNN50 and RMSSD were reduced in the MAC group when compared with the control group (p<0.05 for all). In hypertensive subgroup, all HRV parameters except mean RR interval were diminished in patients with MAC when compared with those without MAC (p<0.05 for all). In non-hypertensive subgroup, all HRV parameters were also diminished in patients with MAC when compared with those without MAC. In the subgroup of patients with coronary artery disease, patients had lower HRV parameters except mean RR interval, pNN50 and RMSSD in comparison to those without MAC (p<0.05 for all). In the subgroup of patients without coronary artery disease, all HRV parameters were depressed in patients with MAC in comparison to those without MAC (p<0.05 for all). Conclusion: Our findings indicate that MAC was associated with reduced heart rate variability which possibly reflects decreased parasympathetic tone with a predominant activity of the sympathetic tone.