Composite coatings of TiB were successfully obtained on the surface of a Ti–6Al–4V alloy by in situ laser cladding technology using Ti/B/Nd2O3 powders. The microstructure and corrosion resistance of the fabricated composite coatings were investigated because relevant studies have been thus far limited in this field. The results indicate that the cladding coating and the substrate combined well via metallurgy after laser cladding treatment, and no obvious cracks were observed in the cladding coatings. The coatings comprise only the TiB and the α-Ti phase. The addition of Nd2O3 promoted the formation of a uniform and refined microstructure of the cladding coatings, and a well-defined structure was obtained when the added Nd2O3 content was 2 wt%. The microhardness of the cladding coating obviously improved by 3 to 4 fold above that of the Ti–6Al–4V substrate. Moreover, the corrosion properties significantly improved by adding Nd2O3 into the coatings. Electrical impedance spectroscopy and polarization tests showed that the best corrosion resistance of the cladding coating was achieved with the addition of 2 wt% Nd2O3. All samples revealed obvious near-capacitive behavior after immersion in a corrosive medium.