It is herein described a contact probe of a testing head of an apparatus for testing electronic devices comprising a probe body being essentially extended in a longitudinal direction between respective end portions adapted to realize a contact with respective contact pads, at least one end portion having transverse dimensions greater than the probe body and comprising an enlarged portion, projecting only in correspondence of a first side wall of the contact probe. Suitably, the at least one end portion further comprises at least one protrusion projecting from a second side wall, opposite to the first side wall and substantially extending toward the second and opposite wall along a longitudinal axis of the contact probe starting from the enlarged portion.