An electromagnetic door lock assembly employs an electromagnet positioned in a frame adjacent to a door, and an adjustable armature assembly positioned in the door for interaction with the electromagnet. The armature assembly includes an armature plate having a pair of shear low-cost, replaceable elements that initially engage the electromagnet. A backing plate is situated adjacent to the armature plate, and a stem coupling the backing plate to the armature plate includes a spring biasing the backing plate and armature plate toward each other. A mounting portion for mounting the armature assembly to a door to be locked is provided with adjusting screws for adjustably positioning the backing plate at a fixed position with respect to the mounting portion so that the armature plate is positioned at a first position for optimum interaction with the electromagnet, the screws having elongated heads for maintaining the relative alignment between the armature plate and the mounting portion as the armature plate moves between the first position and a position contiguous to the electromagnet.