Ventricular arrhythmias play a critical role in chronic heart failure (CHF) and are associated with adverse clinical outcomes. Sleep-disordered breathing (SDB) is associated with arrhythmias and/or a poor prognosis in CHF. Adaptive servo-ventilation (ASV) is a ventilatory support system designed to normalize ventilation in CHF patients with SDB. However, the effects of ASV on ventricular arrhythmias and sympathetic nervous activity are still unclear. Nineteen CHF patients with SDB were examined. We performed simultaneous overnight polysomnography and 24-h Holter ECG monitoring, and measured levels of daily urinary catecholamines for two consecutive days (baseline and on ASV). ASV significantly improved the apnea–hypopnea index (p < 0.01), arousal index (p < 0.01), and mean SpO₂ (p < 0.01), and decreased daily urinary catecholamines (0.466–0.353 mg/day, p = 0.016) compared to baseline. Furthermore, power in the low to high frequency range as a marker of sympathetic nervous activity decreased across a 24-h period (24-h period: 2.8–1.9, p = 0.017; during daytime: 3.7–2.3, p = 0.013; and during sleep time: 1.5–1.3, p = 0.026). Importantly, ASV significantly decreased ventricular premature complexes not only during sleep time but also across a 24-h period (40.5–21.9 beats/h, p = 0.013). The short-term use of ASV reduced ventricular arrhythmias with the attenuation of sympathetic nervous activity, as demonstrated by urinary catecholamines and heart rate variability. ASV may have anti-sympathetic nervous and anti-arrhythmic effects for CHF with SDB.