<p>Titanium and its alloys are commonly used in medical implants but may face wear, corrosion, and bacterial infections over time, compromising their lifespan and biocompatibility. To address these challenges, a multifunctional biocoating was developed based on 3,4-dihydroxyphenylalanine (DOPA) derived from mussel adhesive protein (also known as mussel foot protein, MFP) combined with ferric ions (Fe³⁺). By optimizing the molar ratio of DOPA to Fe³⁺, it was found that a ratio of 3:1 could form a Tri-DOPA–Fe³⁺ complex, which exhibits a quasi-three-dimensional cross-linked structure. This structure reduces the aggregation of protein molecules and produces a large number of cross-linking points between them, thereby improving the uniformity and density of the coating. Consequently, it provides excellent mechanical strength, corrosion resistance, and antibacterial properties. Electrochemical tests showed that the corrosion potential (E_corr) increased by 79.89%, tribological tests showed that the average friction coefficient decreased by 42%, and antibacterial tests showed that the antibacterial rate was close to 100%, and the comprehensive performance was comprehensively improved. Additionally, this coating enhanced the biocompatibility of titanium substrates by forming stable metal coordination bonds between MFP and Fe³⁺ and utilizing positively charged functional groups. As a result, it promoted cell adhesion and growth, with cell proliferation increasing by 64%. The study presents a novel coating method for titanium implant, with promising clinical outcomes.</p> Graphical Abstract <p></p>