OBJECTIVES: Approximately 1 in 400 Albertans has multiple sclerosis (MS). The study’s objective was to determine the real-world impact of adherence to disease-modifying therapies (DMTs) on healthcare utilization and costs among MS patients utilizing administrative data from the Alberta health system in Canada. METHODS: MS patients were identified using a validated case definition (≥1 inpatient record or ≥5 practitioner claims within 2 years) and the study index DMT was defined as the first claim for a DMT between 1April2011 to 31March2014. Treatment adherence (medication possession ratio (MPR) ≥80%), healthcare utilization (including ambulatory care visits, physician claims and hospitalizations) and healthcare costs were explored using multivariable negative binominal regression and logistic regression models. RESULTS: Among 2864 MS patients, 73.8% were female and 61.7% were aged 35-55 years old. Common comorbidities included depression (31%), anxiety (18%), and hypertension (10%). Overall, 66% of the sample were adherent (MPR≥80%). Compared to non-adherent patients, adherent patients had fewer ambulatory care visits (All-cause: 8.8 vs 10.9, p=0.0012; MS-related: 4.3 vs 5.3; p=0.001), physician visits (All-cause: 15.1 vs 18.2, p=0.0001; MS-related: 3.6 vs 4.4; p=0.0001), and hospitalizations (All-cause: 5.2% vs 10.2%, p<0.0001; MS-related: 1.2% vs 2.5%, p=0.0088). After adjusting for potential confounding factors adherent patients had approximately 20% less physician visits (MS-related: IRR 0.82 (0.79,0.86), p<0.0001; All-cause: IRR 0.83 (0.81,0.85), p<0.0001) and ambulatory care visits (MS-related IRR 0.80 (0.77,0.84), p<0.0001; All-cause: IRR 0.82 (0.80,0.84), p<0.0001) and approximately 50% fewer hospitalizations (MS-related: OR 0.50 (0.28-0.89), p<0.0001; All-Cause: OR 0.48 (0.35-0.64), p<0.0001) than non-adherent patients. CONCLUSIONS: Studies assessing the impact of adherence on healthcare resource utilization in MS in Canada are limited. Among MS patients in this Canadian study, non-adherence was associated with increased health system utilization. An understanding of the importance of the impact of adherence on healthcare utilization may lead to more informed decision-making.