An armrest for a chair is provided which has an improved anti-rotation and mechanical connection between an armrest body and a frame tube of the chair. The end of the frame tube is mechanically deformed or is shaped so as to have a non-circular profile with a central opening defined by inwardly projecting arcuate surfaces of the frame tube. The armrest includes a cooperating, non-circular socket which fits onto the frame tube wherein a suitable fastener is threaded downwardly into direct, self-threading engagement with an upper opening formed in the end of the frame tube.