<p>Dovetail mortise-tenon joints are semi-rigid joints that are widely used in ancient timber architecture in China and Southeast Asian countries. Seismic actions are multidimensional, which can cause joints to experience different biaxial loads simultaneously. The forces acting on dovetail joints are complex, and their seismic performance may be compromised under biaxial loading conditions. However, research on the seismic performance of timber beam–column joints subjected to multidimensional seismic actions is lacking. In this study, experiments on dovetail mortise–tenon timber joints subjected to biaxial loads were conducted, simulating diagonal horizontal seismic actions at angles of 45° and 22.5°.The moment–rotation angle curves and tenon pull-out lengths for joints under various loading conditions were obtained from experiments. The experimental results showed that compared with planar joints, the energy dissipation capacity of dovetail mortise–tenon joints subjected to biaxial loads is reduced, and the tenon pull-out length of the joint is significantly increased. It is suggested to reduce the limit value of mortise–tenon joint extraction length in the Chinese standard (GB 50165–2020).</p>