A delivery device for delivering an catheter into an intravenous catheter assembly may include a housing having a distal end, a proximal end, and a slot. The delivery device may include a catheter having a proximal end and a distal end. The delivery device may include a catheter hub disposed within the housing. The catheter may be secured to the catheter hub. A portion of the catheter hub may extend through the slot and may be moveable along the slot to advance the catheter in a distal direction. The distal end of the catheter may be disposed distal to the distal end of the housing when the catheter is advanced.