Efficient design and construction of core-shell heterojunction is regarded as a promising strategy to promote interface electronic transfer for achieving enhanced photocatalytic hydrogen evolution and pollutant degradation. Thus, in this study, a novel core-shell CdIn2S4/Ta3N5 (CIS/TN) nanocomposite photocatalyst was designed and successfully fabricated via the facile in-situ hydrothermal process, where the CdIn2S4 nano-octahedra densely anchored on the surface of Ta3N5 nanoparticles to form the core-shell heterostructure. The as-prepared CIS/TN heterostructures all showed high dual-functional photocatalytic performances for H-2 generation and Methyl Orange (MO) decomposition. Compared with pristine CdIn2S4, the photocatalytic activities of CIS/TN heterostructures were obviously enhanced and the sample CIS/TN-3 with the 3 wt% of Ta3N5 possessed the highest H-2 production of 122.6 mu mol.h(-1).g(-1), which was about 2.43 times as high as that of CdIn2S4 nano-octahedra. Also, it presented the optimal MO photodegradation efficiency (92.2%) and its rate constant was 2.79 times higher than that of pure CdIn2S4. The wonderful dual-functional photocatalytic performance could be attributed to the broad spectral adsorption region and efficient transfer of photoinduced charge carriers between the intimate heterogeneous interface, which would lead to the higher quantum yield and efficiency. The detailed charge transfer path and possible reaction mechanism were also proposed based on the results of trapping experiments and ESR analysis. Our research may provide a direct guidance for developing other highly-efficient Ta3N5-based core/shell heterostructure for energy conversion and environmental governance.