A coupling mechanism for connecting a catheter to a medical infusion line includes a catheter hub arranged on the catheter and a coupling piece arranged at an end of the medical infusion line for connecting with the catheter hub. A pin is axially aligned in the insertion direction of the coupling piece or a sleeve configured for receiving the pin and a locking wedge aligned parallel with the axial extension of the pin or a wedge receptacle for a form-fitting connection of the locking wedge. The wedge receptacle is defined by hinged positive locking elements which are able to move apart from each other. Lever arms are arranged at a distance from each other on the catheter hub or the coupling piece. They interact with the positive locking elements when the coupling mechanism is coupled such that the positive locking elements are spread and the locking wedge is consequently released when the lever arms are actuated.