Abstract: Surfaces of polyetheretherketone (PEEK) were incorporated with carboxyl groups through the plasma treatment with acrylic acid, and then bioactive arginine-glycine-aspartic acid (RGD) peptide was covalently immobilized onto the PEEK surface through a reaction with carboxyl groups. The resulting surface-decorated PEEK was characterized by X-ray photoelectron spectroscopy, water contact angle, surface profiler and mechanical measurements. MC3T3-E1 osteoblast was used as a model cell to evaluate its biocompatibility with the carboxyl group-modified PEEK and RGD peptide-decorated PEEK. The results indicated that carboxyl groups and RGD peptide were successfully grafted onto the surface of PEEK, which led to an improvement in hydrophilicity and surface roughness. Both the plasma treatment and the decoration with RGD peptide seem not to influence the tensile and flexural strength of PEEK, and however they enhanced the interfacial adhesion, spreading and proliferation on osteoblast. PEEK surface decorated with RGD peptide was found to exhibit much better adhesion, spreading and proliferation.