Abstract: A universal trimmer handle assembly for grass trimmers is provided. An exemplary embodiment may include a bolt, a sleeve, a handle, a clamp, and a knob. When the knob is turned in one direction, the bolt squeezes the handle against the sleeve, forces a tapered portion of the sleeve into a tapered groove of the clamp, and squeezes the clamp together around a trimmer shaft. As a result, the handle is prevented from rotating or sliding with respect to the sleeve, the sleeve is prevented from rotating with respect to the clamp, and the clamp is prevented from sliding or rotating with respect to the trimmer shaft. When the knob is turned in an opposite direction, the handle may be rotated or slid with respect to the sleeve and the clamp may be rotated or slid with respect to the trimmer shaft.