Exploring earth‐abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi2S4 yolk‐shell spheres (P‐CoNi2S4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas‐phase phosphorization strategy. Benefiting from the strengthened Ni3+/Ni2+ couple, enhanced electronic conductivity, and hollow structure, the P‐CoNi2S4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of −0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm−2, respectively. Remarkably, when used as the anode and cathode simultaneously, the P‐CoNi2S4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm−2 with excellent durability for 100 h, outperforming most of the reported nickel‐based sulfides and even noble‐metal‐based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea‐rich wastewater treatment. Phosphorus‐substituted CoNi2S4 yolk‐shell spheres (P‐CoNi2S4 YSSs) have been rationally designed and synthesized by a facile hydrothermal sulfidation and subsequent gas‐phase phosphorization strategy. The desired hollow structure and multielement composition with abundant Ni3+ active sites endow P‐CoNi2S4 YSSs with high electrocatalytic activity and robust stability towards electrochemical hydrogen production via water splitting and urea electrolysis.