Abstract This work focuses on the development and validation of a transient one-dimensional numerical model of an active magnetic regenerator (AMR) test apparatus. Simulation results are validated by comparison to room temperature experiments for varying hot heat sink temperature, system pressure, and applied heat load. Three different second-order magnetocaloric materials are used. In addition to external heat leaks, parameters such as thermal conductivity, Curie temperature, and peak magnetocaloric effect are adjusted to obtain better fits to experimental results. In the case of gadolinium, where material properties are well-characterized, the inclusion of parasitic heat leaks as well as an increase in diffusivity resulted in good fits across a broad range of operating conditions. Adjustments to Curie temperature and peak magnetocaloric effect produced good matches with experimental data for Gd0.85Er0.15. Predictive simulations of a Gd – Gd0.85Er0.15 two-layer regenerator are briefly discussed.