This study evaluated disease activity in people with Multiple Sclerosis (PwMS) who received immune checkpoint inhibitors (ICIs) compared to PwMS not treated with ICIs. There were 108 PwMS included (27 PwMS+ICIs and 81 PwMS controls), matched on age, sex, disease duration, DMTs, and MS disease course. Of 27 PwMS+ICIs, one (4%) had a relapse and four (15%) developed new MRI lesions without clinical symptoms. Time to relapse and MRI activity were compared using Kaplan-Meier curves and Cox regression models. There was no significant difference for either time to relapse (p = 0.34) or MRI activity (p = 0.15) in PwMS+ICIs compared to controls.