Provided is a button fastener, having a penetrating part (10) and a receiving part (20), wherein the penetrating part (10) is substantially u-shaped by means of having a transversal base (16) with two parallel legs (15), each of said legs (15) having a pointed end (11; 31) and a protruding retaining member (14;34) adjacent said pointed end arranged to interlock with the receiving part (20), and wherein said receiving part (20) is substantially u-shaped with at least one transversal base (25) and at a position at a distance from said transversal base (25) an interlocking receiving member (22) arranged to interlock with said penetrating part (10), wherein at least one of said parts (10, 20) is arranged with a gripping member (19, 29) which is detachable by means of a line of rupture (17, 27), and a method of fastening buttons.