Abstract: A coupler is provided which is mountable to a fitting of a breakaway coupling to facilitate assembly and disassembly of the coupling. The coupling has a first fitting and a second fitting which are held together by a ball in the first fitting which is received in a detent in the second fitting. The second fitting has an outer sleeve on which the detent is formed, and an inner sleeve slideable in the outer sleeve. A latch ring on the inner sleeve is alignable with the groove. A spring biases the inner sleeve and latch ring into a locking position in which the detent balls are urged into engagement with the detent to hold the two fittings together. The coupler includes an open ended housing having a side wall and an end wall. A plate, securable to the second fitting inner sleeve, is received in the coupler housing for axial movement. A cam on an outer surface of the housing end wall is connected to the plate by a rod.