Objectives In year 2016, Danish national guidelines included a mandatory switch of patients with inflammatory rheumatic diseases treated with originator etanercept (ETA) to biosimilar SB4 in routine care. We aimed to explore if switching lead to increased healthcare utilisation and costs. Methods Observational cohort study. Adult patients who switched from ETA to SB4 were identified in the Danish nationwide DANBIO registry. In the National Patient Registry, we identified health utilisation (hospital admissions/hospital days/outpatient visits/prescription medication use) and comorbidities. Estimation of health utilisation included average use and costs 1 year before/after switch, changes after the switch, and whether patient characteristics affected changes. Analyses were by adjusted two-step gamma distributed regression models, and for changes over time a generalized estimation equations (GEE) model was applied. Impact of comorbidities was explored as interaction terms in the model. Medication costs of ETA and SB4 were not included in model. Results 1620 patients were included (mean age 55 years (SD 14.7), 40% male). Costs before and after switching were mainly driven by outpatient visits (67%/72% of all costs). Monthly fluctuations of costs were similar before/after switch. After switching, use (8%) and costs (7%) of outpatient services increased, whereas costs of admissions (55%) and medication (5%) decreased. Patients with longer ETA treatment duration had an increase in use and costs of healthcare resources, whereas gender and comorbidities had no impact. Higher age was associated with an increase in costs of inpatient services. Conclusion We demonstrated no obvious changes in overall use and costs of healthcare services following switch from originator to biosimilar etanercept.