The design and synthesis of advanced semiconductors is crucial for the full utilization of solar energy. Herein, colloidal selective‐epitaxial hybrid of tripartite semiconducting sulfides CuInS2Cd(In)SMoS2 heteronanostructures (HNs) via lateral‐ and vertical‐epitaxial growths, followed by cation exchange reactions, are reported. The lateral‐epitaxial CuInS2 and Cd(In)S enable effective visible to near‐infrared (NIR) solar spectrum absorption, and the vertical‐epitaxial ultrathin MoS2 offer sufficient edge sulfur sites for the hydrogen evolution reaction (HER). Furthermore, the integrated structures exhibit unique epitaxial‐staggered type II band alignments for continuous charge separation. They achieve the H2 evolution rate up to 8 mmol h−1 g−1, which is ≈35 times higher than bare CdS and show no deactivation after long‐term cycling, representing one of the most efficient and robust noble‐metal‐free photocatalysts. This design principle and transformation protocol open a new way for creating all‐in‐one multifunctional catalysts in a predictable manner. A wet‐chemical strategy for the selective‐epitaxial hybrid of unique tripartite semiconducting sulfide heteronanostructures CuInS2Cd(In)SMoS2 is reported. The stepwise integrated structures demonstrate superior solar‐to‐hydrogen conversion performance due to the enhanced capabilities for solar absorption and charge separation, together with sufficient catalytically active sites.