Hydrogen leakage in storage and transport presents critical safety challenges, especially under cryogenic conditions. Under such conditions, hydrogen jets experience strong expansion, rapid cooling, and significant density variations, which govern jet spreading, mixing, and far-field plume development. This study examines how real-gas thermodynamic effects influence these physical processes in cryogenic hydrogen jets, and evaluates the extent to which ideal-gas assumptions remain valid as the flow evolves downstream from the injection region. The solver employs a Large Eddy Simulation (LES) framework with a quasi-dynamic subgrid-scale kinetic-energy model [1]. An entropy-stable formulation coupled with the Double-Flux method [2] ensures consistent treatment of multi-component flows with variable specific-heat ratios while satisfying a semi-discrete entropy inequality. Fluxes at cell interfaces are evaluated using a robust approximate Riemann solver, and explicit Runge–Kutta time integration enables high-fidelity resolution of supersonic flow features. Multicomponent advection and diffusion are fully accounted for, while combustion is neglected due to temperatures well below hydrogen’s auto-ignition threshold. Validation of the solver’s real-gas modeling is carried out against high-speed cryogenic jet experiments at the Karlsruhe Institute of Technology (KIT) [3]. Simulations are performed for a range of cryogenic temperatures (30–85 K) to assess the impact of real-gas thermodynamics on hydrogen plume behavior. Strong agreement with experimental measurements is observed in the near field, while far-field plume evolution and mixing are largely captured using ideal gas assumptions, highlighting that real-gas effects are most pronounced close to the injection region. This work provides insight into the role of real-gas thermodynamics in cryogenic hydrogen jets, supported by strong agreement with experimental data. The results clarify the spatial extent over which real-gas effects must be considered and demonstrate the reliability of ideal-gas modeling in the far field.