PROBLEM TO BE SOLVED: To provide an introducer assembly formed by integrating an introducer sheath with a dilator beforehand, maintaining the blood stop performance of a blood stop valve over a long period of time and causing no hindrance to the original function of a dilator tube.SOLUTION: The introducer assembly is configured to insert the dilator tube 50 through an insertion part 41 of the blood stop valve 40 and to integrate the introducer sheath 11 with the dilator 13 beforehand. When a cap 12 is pressed toward the base end face of a sheath hub 30 and locked to the sheath hub, a deformation member 90 disposed between the blood stop valve and the cap 12 presses the blood stop valve to apply, to the blood stop valve, compressive force in a direction to put the insertion part into a blocked state.
