OBJECTIVE: To assess the determinants of heart rate (HR) and heart rate variability (HRV) in children. The autonomic nervous system as measured by HR and HRV is considered a biological marker of psychopathology in children. METHODS: We examined the relationship of maternal psychopathology with infant HR and HRV. HR was recorded at 14 months in 528 infants. The high-frequency component of HRV was used as an indicator of cardiac vagal modulation. The presence of a lifetime maternal psychiatric diagnosis was assessed with the Composite International Diagnostic Interview. Presence of maternal psychiatric symptoms during pregnancy and 2 months after birth was assessed, using the Brief Symptom Inventory. RESULTS: A maternal history of a psychiatric disorder was associated with a 0.24-standard deviation (SD) higher mean HR in the infant (beta = 0.24, 95% Confidence Interval (CI) = 0.03, 0.4, p = .025) and a 0.14-SD lower high-frequency power (beta = -0.14, 95% CI = -0.6, -0.03, p = .003). Likewise, postnatal maternal anxiety and depression symptoms were associated with infant mean HR. A 1-point increase in the mean anxiety symptom score was associated with 0.14-SD higher mean HR in the infant (beta = 0.14, 95% CI = 0.05, 0.2, p = .004), and a 1-point increase in mean depression score with a 0.11-SD increase (beta = 0.11, 95% CI = 0.01, 0.2, p = .025). No significant associations of prenatal maternal affective symptoms with infants autonomic functioning were found. CONCLUSION: Maternal lifetime psychiatric diagnosis and postnatal psychiatric symptoms are associated with infant autonomic functioning, namely, higher mean HR and lower vagal modulation.