This letter presents a method for deembedding reciprocal three-port devices, which operates directly on S-parameters and does not rely on any absolute load resistances. A set of two-port test structures, involving only the device under test (DUT) itself and reflection terminations (open or short), is required. The process is demonstrated with two integrated wideband balun designs, operating between 140 and 220 GHz, each using a set of three test structures with four DUT dummies total. The gathered results indicate an excellent match with the simulations with a deviation in amplitude below 1 dB and phase difference below 5°.