Abstract The shear plate dowel joint (SPDJ) is a novel connection design for heavy timber structures. The connection uses a single large diameter dowel and glued-on steel plates to transfer loads between members. Consequently, the design of the dowel is of great influence for the global performance of the connection. This paper presents an experimental and numerical investigation of the influence of the geometry and the material parameters of the dowel, focusing on the possibility to design the joint for ductile failure modes. The study is conducted for a single-member node configuration as well as a three-member node configuration. Testing was conducted on dowels made of steel, aluminium, birch and laminated densified wood, and shear plates of steel and plywood. It is shown that ductile deformations of the SPDJ can be increased by 30–80% using thin-walled metal dowels. The results show that most of the tested wood-based materials are inadequate for such detailing, except laminated densified wood. The numerical study is focused on the ductile response obtained when using steel tubes as the load transferring dowel. The optimal ratio of dowel outer diameter D o to steel plate size is found to be 0.30–0.35, using a tube wall thickness of approximately 0.075 D o . Using this geometry, a good balance between load carrying capacity and ductile behaviour is obtained.