The invention relates to an assist arm intended to be fitted on an exoskeleton, having a mounting plate (2) carrying a drive member (20), a shoulder segment (4) articulated on the mounting plate, an arm segment (6) having a proximal end articulated on the shoulder segment, a forearm segment (8) having a proximal end articulated on a distal end of the arm segment, an actuating cable (27) driven by the drive member and forming two strands (27a, 27b) which extend parallel to the first axis in order to pass through the first articulation and to wind around a receiving pulley (30) which is mounted in a rotating manner about the second axis and which rotates as one with the arm, and connecting means (31, 32, 33) coupled between the shoulder segment and the forearm second segment and arranged such that a flexion of the arm segment causes a concomitant flexion of the forearm segment.
