A grommet and a wire harness with a grommet are provided. The grommet is for attachment to the joint between tube members into which electrical wires are inserted, and includes a main body portion that is formed by a material that has elasticity and is shaped as a tube capable of coming into close contact with the tube members. The main body portion has a pair of divided bodies that are obtained dividing the main body portion such that the interior of the main body portion is open over the entire length thereof. Mating surfaces of the pair of divided bodies are fixed to each other in a liquid-tight manner.