The frequency of switches between Disease Modifying Therapies (DMTs) in Multiple Sclerosis (MS) has increased considerably over previous years. Between fingolimod and anti-CD20 therapies, a 1-month washout period is usually recommended. However, disease reactivations are frequent after fingolimod (Fg) cessation. Using a retrospective observational monocentric exposed/non-exposed cohort study, we investigated the efficacy and the safety of a shorter washout period (WP) between Fg and anti-CD20. We compared two groups: 25 patients with a short WP (<21 days) and 20 patients with a longer WP (>21 days). We observed no reactivation during WP in patients with a short WP against a relapse in 55% of patients in the longer group. Moreover, clinical and biological safety was excellent. Based on these findings, we recommend a shorter WP between fingolimod and anti-CD20 therapies in MS.