Etanercept is a recombinant fusion protein approved for the treatment of TNF-α mediated diseases such as rheumatoid arthritis (RA), psoriasis, psoriatic arthritis, and ankylosing spondylitis. Herein, we present an evaluation of the physicochemical and biological properties of a biosimilar etanercept and its reference product followed by a clinical study in patients diagnosed with RA intended to demonstrate comparability of their immunomodulatory activity. Identity analyses showed a total correspondence of the primary and higher-order structure between the two products. In regard to intrinsic heterogeneity, both products showed to be highly heterogenous; however the biosimilar etanercept exhibited similar charge and glycan heterogeneity intervals compared to the reference product. Apoptosis inhibition assay also showed that, despite the high degree of heterogeneity exhibited by both products, no significant differences exist in their in vitro activity. Finally, the clinical assessment conducted in RA-diagnosed patients did not show significant differences in the evaluated pharmacodynamic markers of both products. Collectively, the results from the comparability exercise provide convincing evidence that the evaluated biosimilar etanercept can be considered an effective alternative for the treatment of RA.