The same aggressive treatments that have led to a reduction in the breast cancer may also have adverse effects on cardiac autonomic balance. The objective of this study was to compare heart rate variability (HRV) between breast cancer survivors in the first year posttreatment and healthy women, controlling for known confounders. This descriptive case-controlled study included 22 breast cancer survivors and 22 healthy age- and sex-matched controls. Short-term HRV was measured using an accepted methodology to assess the cardiac autonomic balance. One-way analysis of covariance results revealed that heart rate was significantly higher (F = 15.86, p < .001) and the standard deviation of normal-to-normal (NN) interval (F = 19.93, p = .001), square root of mean squared differences of successive NN intervals (F = 18.72, p = .001), HRV index (F = 5.44, p = .025), and high-frequency (F = 5.77, p = .03) values were significantly lower in the breast cancer survivors than in the matched controls. The principal finding of the presence of a cardiovascular imbalance in breast cancer survivors in comparison to healthy age-matched controls suggests that HRV study could be a clinically useful tool to detect cardiovascular disease in early-stage breast cancer survivors.