A type of assembled joints for timber column-reinforced concrete hybrid structures was designed to study the nonlinear mechanical properties of beam-to-column flexible joints for assembled timber column-reinforced concrete hybrid structures. A finite element model was established by using the ABAQUS finite element software, and the analyses under monotone loading and low-cycle repeated loading were conducted for the model. Effects of rubber hardness and vertical load on the nonlinear mechanical properties of assembled joints, including the damage characteristics, hysteresis curve, skeleton curve, bearing capacity, and energy dissipation capacity,were mainly studied. Compared with related literature, the feasibility of the proposed method was verified. Results show that the main failure modes of the flexible joint are compression buckling and tension lifting of the column base and compression deformation of rubber. The bearing capacity, stiffness, and ductility of the flexible assembled joint are proportional to the hardness of filled damping materials. The lateral tilting of columns and the lifting of column bases are effectively limited by the increase in the hardness damping materials. When rubber materials with 71 HA hardness are used, their energy dissipation capacity is good. Meanwhile, the vertical load has a considerable influence on the damping ratio of the assembled joint, which effectively improves the viscous damping ratio of the assembled joint by increasing the vertical load.