A catheter assembly includes a catheter and a dilator. The catheter has a first curved portion at a front end portion thereof. The dilator includes a protruding portion, a low stiffness portion, and a high stiffness portion. The protruding portion is arranged on a front end portion of the dilator. At least part of the protruding portion protrudes from a front end of the catheter when the dilator is inserted into the catheter. The low stiffness portion is arranged on a rear side of the protruding portion and at a position corresponding to the first curved portion of the catheter, and has a lower flexural stiffness than the protruding portion. The high stiffness portion is arranged on a rear side of the low stiffness portion and has a higher flexural stiffness than the low stiffness portion.
