As we all know, more than half of the solar spectrum is near infrared (NIR) light. However, NIR light is seldom utilized in photocatalytic reactions. In this work, the W₁₈O₄₉/g-C₃N₄ heterojunction catalyst is prepared and used for full-spectrum-driven N₂ photofixation from the UV to the NIR region for the first time. X-ray diffraction, N₂ adsorption, UV-Vis-NIR spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence, X-ray photoelectron spectroscopy and electrochemical impedance spectra were used to characterize the prepared catalysts. The result indicates that the as-prepared W₁₈O₄₉/g-C₃N₄ heterojunction catalysts display much higher N₂ photofixation performance than individual W₁₈O₄₉ or g-C₃N₄, which should be due to the improved separation rate of electron–hole pairs. g-C₃N₄ is the active component in the catalyst for N₂ photofixation. W₁₈O₄₉ plays the role of a light absorber in the full-spectrum to form more photogenerated electrons for recombining the holes in g-C₃N₄ through the “Z-scheme” mechanism. A possible electron transfer route is proposed.