Photocatalysis is one of the most promising technologies owing to its great potential to relieve energy and environmental issues. Constructing Z-scheme heterojunction photocatalyst with strong redox ability to make for enhanced light absorption and efficient charge separation is extremely attractive but still underdeveloped. Herein, Z-scheme heterojunction of CuInS2/g-C3N4 with a "sheet-on-sheet" hierarchical structure showing enhanced photocatalytic performance for the tetracycline (TC) degradation under visible-light irradiation has been developed. This 2D/2D hierarchical structure of CuInS2/g-C3N4 composite not only enlarges the contact region in the heterojunction interface but also provides more active reaction sites, as demonstrated by the TEM and BET analyses. Particularly, 50 wt% CuInS2/g-C3N4 heterojunction shows the highest photocatalytic activity (20 mg/L; 83.7% degradation within 60 min), which the apparent rate constant is 15 and 11 times higher than that of pure g-C3N4 and CuInS2 nanosheets, respectively. The remarkably enhanced photocatalytic activity mainly derives from the synergistic effect between CuInS2 and g-C3N4, thereby promoting the charge separation during the photocatalytic reaction. This work is expected to provide a design idea to construct multifunctional 2D/2D nanocomposites for photocatalytic applications.