A transcatheter atrio-ventricular valve prosthesis (1) for functional replacement of an atrio-ventricular valve (9) in a connection channel (18), having a circumferential connection channel wall structure (18'), between an atrial chamber (3) and a ventricular chamber (5) of a heart (7), comprising an inner device (19) configured to be disposed in an interior of the connection channel (18), the inner device (19) having a circumferential support structure (21) which is radially expandable, and having a valve (22) attached to the circumferential support structure (21), wherein the circumferential support structure (21) of the inner device (19) is of tubular shape and extends along an axis and has two axial ends (21', 21"), wherein the inner device (19) is to be arranged with its circumferential support structure (21) within the native valve annulus or at an interior position close thereto and in-between the native valve leaflets (11), and an outer device (25) configured to be disposed on the exterior of the connection channel (18), wherein the outer device is configured to at least partly extend around the inner device (19) at a radial distance to the inner device (19), and wherein the inner and outer devices (19, 25) are configured to form a securing mechanism for securing the circumferential connection channel wall structure (18') therebetween. In detail, the outer device is configured to form a ring (26) and the circumferential support structure of the inner device comprises an outer circumferential groove (35), wherein the ring is configured to be aligned to the groove and engage it with the connection channel wall structure clamped therebetween.