The warm forming of a door panel made of commercial grade ZEK100 magnesium alloy sheet was modelled using finite element techniques (Autoform). The operation consisted of a heating step, a forming step and a cooling/springback step. The material properties of the ZEK100 blank were modelled using a set of temperature- and strain rate-dependent stress-strain curves, which were derived based on a Zerilli-Armstrong constitutive model. In order to simplify the material model to enable its complex response to be represented within a commercial finite element code, the anisotropy of the magnesium sheet was approximated using a Banabic-2005 yield surface and yield asymmetry was neglected, a reasonable approach for warm forming. Necking was predicted using a set of forming limit curves obtained at different isothermal temperatures. The entire forming model was run at a punch speed of 160 mm/s, and two initial blank temperatures: 215 and 230 degC. The tooling was initially at room temperature. The model predicted that the blank cracked when its initial temperature was 215 degC due to excessive cooling. The best formability (lack of wrinkling and necking) was predicted when the blank was heated to 230 degC. These predictions agree well with the forming trial outcomes.