In order to further improve the corrosion resistance of commercial pure titanium (CP–Ti), the ex-situ formed Ti-5 wt.% TiN composite was developed by selective laser melting (SLM) and the corrosion behavior of the SLM-produced CP-Ti and Ti-5 wt.% TiN composite in 0.5 M HCl solution was investigated. The results show that the Ti-5 wt.% TiN composite consists of α′-Ti, δ-TiN and ε-Ti2N, where the acicular α′ martensite (∼0.73 μm) is much smaller than that (∼1.37 μm) in the CP-Ti. The passive film formed on the surface of the Ti-5 wt.% TiN composite and CP-Ti is mainly composed of TiO2. However, the Ti-5 wt.% TiN composite exhibits higher corrosion resistance than the CP-Ti, which is attributed to the fact that TiN as the micro-cathode preferentially induces the composite to enter the passivation state. The immersing tests also confirmed that the addition of 5 wt% TiN can efficiently improve the corrosion resistance of CP-Ti.