A turbine engine assembly including a first rotor element and a second rotor element extending around a longitudinal axis X and coupled to one another by a gear coupling, the first rotor element including teeth and the second rotor element including complementary teeth which extend along the longitudinal axis and form the gear coupling. The first and second rotor elements each include a first and a second radial flange which are annular and arranged facing one another, and the assembly includes a sealing device configured to ensure that the gear coupling is sealed at the first and second flanges.