Fingolimod exerts its therapeutic effect in multiple sclerosis by modulating sphingosine-1P receptors which are expressed in the heart mediating fingolimod first dose effects. Understanding potential interactions of baseline characteristics and autonomic profile with fingolimod first dose effects may add novel safety information and help explain cases requiring extension of the 6-hour ECG monitoring period. We aimed at characterizing the patient population treated with the first dose of fingolimod in clinical practice in an observational, multicenter, prospective 6-hours (up to 24) study. ECG was recorded for 15 min before first fingolimod administration and for 6 h after. Heart rate (HR) and HR variability in the frequency domain were derived from ECG traces. Out of the 625 enrolled patients, 580 (92.8%) were discharged at the sixth hour after fingolimod first dose; 45 (7.2%) required monitoring extension. Data confirm the well characterized cardiovascular fingolimod profile upon treatment initiation. Ten (1.6%) patients showed an atrioventricular block, all asymptomatic and self-resolving. Normalized spectral power in the High Frequency band (marking vagal modulation) and previous annualized relapse rate were independently correlated with the probability of undergoing extended monitoring. Our results could provide useful information for the stratification and individualized monitoring of MS patients prescribed with fingolimod.