Background: Dimethyl fumerate (DF) is a first line therapy for relapsing remitting multiple sclerosis (RRMS). This retrospective cohort study aims to determine adverse events (AEs) after initiation of DF in a real world clinical setting. Methods: Data from patients at the Calgary MS Clinic with RRMS who initiated DF between July 1, 2013 and December 31, 2014 were analyzed. Demographic, clinical and lab information were collected from patient electronic medical records and the clinic database. Results: This analysis included 170 patients. At treatment initiation mean age was 42.1 years, 75% were women, mean disease duration was 12.5 years, median EDSS was 2.0, and 24% were treatment naïve. Median follow-up was 6.4 months (range: 1.5-17.7). AEs occurred in 101 (59%); the most common were flushing (31%), gastrointestinal (GI) side effects (24%), and elevated liver enzymes (18%). Other less frequent AEs included lymphopenia (lymphocyte count < 0.5) (4%) and proteinuria (4%). DF was discontinued by 17 (10%); median time to discontinuation was 3.1 months. Fifteen (9%) discontinued due to AE. Conclusions: AE associated with DF in a real world clinical setting is comparable to the Canadian monograph for flushing, GI side effects, and lymphopenia but lower for elevated liver enzymes and proteinuria.