This study was aimed at comparing the biomechanical performance of personalised 3D-printed clavicle plates of different materials to treat midshaft clavicle fractures with the finite element (FE) method. The FE model of a fractured clavicle with a personalised 3D-printed clavicle plate and screws was constructed. Three types of materials were simulated, including stainless steel, titanium alloy, and magnesium alloy. Two loading conditions (axial compression and inferior bending) were applied at the distal end of the clavicle to simulate arm abduction. Plate stiffness, peak stress, and bone strain at the clavicle fracture site were measured and compared. The stiffness of the stainless steel clavicle plate was significantly greater than that of the titanium alloy clavicle plate. The stiffness of the magnesium alloy clavicle plate was similar to that of the intact clavicle; peak stress of the magnesium alloy clavicle plate was the lowest; thus, it had less stress-shielding effects on bone formation. The magnesium alloy clavicle plate was more likely to form bone by distributing proper strain at the clavicle fracture site. According to the influence of different materials on the tensile strength, magnesium alloy clavicle plates might be preferred owing to their bionic stiffness in the treatment of patients with a low risk of falling. For patients who engage in contact sports, a titanium alloy clavicle plate might be more suitable.