A cable routing assembly, disposed on a headset of a bicycle and having a through hole fitting around a steerer tube of the bicycle, includes a top annular base having a first through hole and a first cable groove and a bottom annular base having a second through hole and a second cable groove. When the top annular base is engaged with the bottom annular base, the top annular base and the bottom annular base jointly form an internal space, and the first cable groove and the second cable groove jointly surround to form a cable channel communicating between an external space and the internal space. The first through hole communicates with the second through hole to form the through hole. An axial direction and a channel direction that are not parallel are defined. The through hole extends along the axial direction. The cable channel extends along the channel direction.