Achieving a high photocatalytic activity toward photoelectrochemical (PEC) water splitting has become a formidable challenge for titanium oxide (TiO2) owing to its poor photoresponse to visible light and low electrical conductivity. Herein, we report the first demonstration of nonmetal TiN as a plasmonic booster to significantly enhancing the PEC water splitting performance of TiO2. A unique multiscaled architecture organized by interweaving hollow microfiber monolith and hierarchical TiN/N-TiO2 nanorod arrays is fabricated by a facile seamless nitridation process. The conductive TiN not only affords plasmon resonance on the N-TiO2 to enable high photoactivity in a broadband UV-vis light region, but also assists in the charge generation-separation-transportation-injection efficiency of TiO2 for enhanced water oxidation kinetics. The TiN/N-TiO2 heterostructure manifests an unprecedented high and durable photocurrent density of 3.12 mA cm(-2) at 1.23 V (vs. reversible hydrogen electrode (RHE)) under standard AM 1.5 G illumination and substantiates an outstanding visible-light-driven photocurrent density of 1.63 mA cm(-2) without the use of any hole scavenger and cocatalysts. This study will enrich the fundamental understanding of nonmetal plasmonic effect in and beyond the field of PEC water splitting.