Early bereavement is associated with increased cardiovascular events. The mechanism, however, has not been well studied. We assessed whether bereavement is associated with an increased heart rate (HR) and decreased heart rate variability that might contribute to increased cardiovascular risk. A total of 78 bereaved spouses and parents (55 women and 23 men; aged 34 to 87 years, mean 65) were studied with 24-hour Holter monitoring within 2 weeks of bereavement (acute) and at 6 months. Their findings were compared to those from a nonbereaved reference group (52 women and 27 men) aged 33 to 91 years (mean 63.6). All participants were in sinus rhythm. We assessed the mean HR, atrial and ventricular arrhythmias, and both time and frequency domain heart rate variability measures. Acute bereavement was associated with increased 24-hour HR (mean ± SE, 75.1 ± 1.1 vs 70.7 ± 1.0; p = 0.004) and reduced heart rate variability, as indicated by lower standard deviation of the NN intervals index (median 45.4 vs 49.9, p = 0.017), total power (7.78 ± 0.10 vs 8.02 ± 0.09, p = 0.03), very low frequency (7.23 ± 0.09 vs 7.44, p = 0.046) and low frequency (5.76 ± 0.12 vs 6.16 ± 0.09, p = 0.01). At 6 months, the bereaved had a significantly lower HR (p = 0.001) and increased standard deviation of the NN intervals index (p = 0.02), square root of the mean square of differences of successive intervals (p = 0.045), number of interval differences of successive NN intervals >50 ms divided by the number of NN intervals (p = 0.039), low-frequency power (p = 0.02), and high frequency (p = 0.002) compared to the initial acute levels. In conclusion, the present study, the first to report 24-hour HR monitoring in the early weeks of bereavement, has demonstrated increased HR and altered autonomic function that might contribute to the increased cardiovascular events in early bereavement.