The current research focuses on analyzing the magnetic and magnetocaloric properties of REH2(RE=Gd,Tb,Dy) in a CaF2-like face-centered cubic system. Through the application of first-principles calculations and Monte Carlo simulations, the following physical parameters are determined: Adiabatic temperature change, isothermal entropy change, and relative cooling power (RCP). The magnetic moments of Gadolinium, Terbium, and Dysprosium calculated by the PWSCF method are 6.76μB, 5.74μB, and 4.65μB respectively, aligning well with experimental results. The compounds underwent a second-order phase transition from antiferromagnetic to paramagnetic at TN=21.7K, 17.6K, and 4.3K respectively for GdH2, TbH2, and DyH2. The isothermal entropy change (−ΔSMmax) reached a maximum value of −11.75J/kg.K, −12.47J/kg.K, and −12.87J/kg.K for GdH2, TbH2, and DyH2 under a magnetic field of 5T. We found also that the hydrogenation of rare earth reduces its magnetic performance while but it enhances its thermodynamic and mechanical stability. Display omitted •The thermodynamic and mechanical stability of REH2(RE=Gd,Tb,Dy) compounds are investigated.•The REH2 compounds are metals with an antiferromagnetic state.•The magnetocaloric property values of REH2 compounds indicate that they are potential for low-temperature magnetic refrigeration applications.•Comparing the properties of Gd with REH2 compounds reveals the role of hydrogen in these materials.