Ta₃N₅ is a very promising visible-light-driven photocatalyst for water splitting and organic degradation. However, the low photocatalytic activity and poor photostability limit its application. To enhance the photocatalytic performance of Ta₃N₅, we prepared core-shell Ta₃N₅@polyaniline (PANI) by a chemisorption process. The effect of PANI content on the microstructure, optical, photoelectrochemical property and the photocatalytic activity of the samples were studied. The results showed that after the adsorption process, PANI was successfully coated on Ta₃N₅ with intimate contact and could significantly enhance the photocatalytic performance. The PANI shell thickness dramatically affected the photocatalytic activity. The Ta₃N₅@PANI 2 (PANI shell thickness: 0.9 nm) possessed the highest visible light photocatalytic H₂ production rate of 72.6 μmol g⁻¹ h⁻¹ and RhB degradation rate of 0.041 min⁻¹, which were 3.2 and 16.6 times higher than those of Ta₃N₅. The Ta₃N₅@PANI exhibited excellent photostability and reusability. The superior photocatalytic performance of the Ta₃N₅@PANI was attributed to the synergic effect, including the intense interfacial interaction, enhanced visible light absorption, efficient charge separation and corrosive holes transfer from Ta₃N₅ to PANI. Furthermore, DFT calculations were applied to explore the interfacial interaction between PANI and Ta₃N₅. This study suggests that PANI modification can improve the photocatalytic application of Ta₃N₅ for H₂ production and RhB degradation.