A catheter assembly includes an inner needle having a sharp tip at a distal end thereof a catheter in which the inner needle is disposed a catheter hub disposed on a proximal end side of the catheter and through which the inner needle is insertable an inner needle hub disposed on a proximal end side of the inner needle and a protector mounted detachably on the inner needle hub, the protector being configured to cover at least the tip of the inner needle. The protector includes a movement prevention unit, the movement prevention unit being configured to prevent movement of the catheter toward the tip with respect to the inner needle in a state in which a distal end side of the inner needle protrudes a predetermined length from the catheter.
