Abstract Objective: To compare the effectiveness and safety of original (Enbrel®) and biosimilar (Benepali®) etanercept in Biologic Disease-modifying Antirheumatic Drug (bDMARD)-naïve patients, measured by persistence rates over 36 months of follow-up. Methods: A retrospective multicentre observational study using data collected prospectively from The Rheumatic Diseases Portuguese Registry (Reuma.pt) was performed, including patients with: age ≥ 18 years old; diagnosis of Rheumatoid Arthritis (RA), Psoriatic Arthritis (PsA) or Spondyloarthritis (SpA) (axial or peripheral) with active disease and biologic-naïve who initiated treatment with etanercept as the first line biological treatment after 2010. Kaplan-Meyer and Cox regression were used to calculate the persistence rate in treatment. Disease activity at baseline and follow-up data at 6, 12, 18 and 24 months of treatment were compared. Causes for discontinuing therapy were summarized using descriptive statistics. Statistical significance was assumed for 2-sided p-values <0.05. Results: We included 1693 patients (413 on Benepali® and 1280 on Enbrel®): 864 diagnosed with RA, 335 with PsA and 494 with SpA. The 3-year persistence rates were not significantly different between both treatment groups in RA, PsA and SpA patients. In the adjusted Cox model, hazard ratios of discontinuation were not statistically different (p>0.05). The proportion of subjects in remission or low disease activity in each disease was similar in both groups. Overall, 535 (31.6%) patients discontinued etanercept (428 patients on Enbrel® and 107 patients on Benepali®). The major cause of discontinuation was inefficacy (57.8%). No differences for the occurrence of inefficacy or adverse effects were found between treatment groups. Conclusions: Benepali® and Enbrel® demonstrated similar effectiveness and safety in RA, PsA and SpA in our cohort of patients. These data corroborate that the original and biosimilar drugs have similar quality characteristics and biological activity.