A windscreen wiper arm, particularly for automobiles, that is able to oscillate upwardly and downwardly between a downward position and an upward position. One end of the windscreen wiper arm is adapted to be pivotally connected to a mounting head mounted on a drive shaft. Another end of the windscreen wiper arm is rigidly connected to an adapter adapted to be connected to an elongated wiper blade to be placed in abutment with a windscreen to be wiped. A joint part is adapted to be interposed between the adapter and the elongated wiper blade. The adapter, at the location of its connection to the wiper blade, has a U-shaped cross-section with a base and two spaced-apart legs. The windscreen wiper arm is provided with a nozzle for spraying a washing liquid onto the windscreen to be wiped. The nozzle is detachably connected to the adapter. At least one protrusion of the nozzle engages into a corresponding hole in one of the legs of the U-shaped cross-section of the adapter. The protrusion extends inwardly in a direction towards the adapter. The protrusion has a shank passing through the hole, and an enlarged head abutting an inner wall of the leg provided with the hole. The joint part is provided with a slit in which the enlarged head rests for blocking any movement of the protrusion in a direction towards the windscreen to be wiped and in a direction away from the windscreen to be wiped.