Segment of an articulated arm made of composite material, with an elongated shape defining a longitudinal axis, and having a box-like cross section. The segment includes a first end portion, configured for the pivoting of a further segment, a second intermediate portion configured for the pivoting of an actuation member, and a third end portion. The first, second and third portions are made in a single body. The second intermediate portion includes a protruding zone defined by a first side and by a second side converging with respect to each other to define a top. Pivoting elements are provided in the protruding zone for the pivoting of the actuation member between the protruding zone and the first end portion. The first and the second side defining the protruding zone are filleted to substantially rectilinear adjacent tracts of the first and third end portions.