An assembly (1) for detecting the wear of a brake pad of a disk brake, wherein said assembly comprises at least one sensor body (2) and at least one spring (4), said assembly being suitable for cooperating with said pad (10) which comprises a support plate (11), suitable for being supported by the disk brake, and to which there is associated friction material (12), suitable for to coming into contact with braking surfaces of a disk-brake disk, and wherein said at least one sensor body (2) is coupled geometrically to said support plate (11), said at least one spring (4) surrounding said at least one sensor body (2) so that said at least one spring (4) is positioned in said geometric coupling between said at least one sensor body (2) and said plate (11) and presenting projections (41) for the snap-coupling to said support plate (11), and wherein said at least one spring (4) has indentations (42) bent towards the at least one sensor body (2) for constraining said at least one spring (4) to said at least one sensor body (2), wherein said indentations (42) comprise end or terminal sections (43) of the spring with at least one of their edges (44) facing towards the at least one body (2).