A mixing valve has a housing, a valve cartridge fixed in the housing and having valve elements movable to vary rate and temperature of flow through the cartridge, and a handle connected to the valve elements and movable through a predetermined angular displacement about a temperature-adjustment axis to vary the temperature of flow through the cartridge and a flow-adjustment axis orthogonal to the temperature-adjustment axis to vary the rate of flow through the cartridge. A sleeve-like casing surrounding the cartridge is rotatable on the housing about one of the axes and is traversed by the handle. Interengaging formations on the casing and on the housing axially retain the casing on the housing except in a predetermined angular position of the casing on the housing relative to the one axis. The predetermined angular position corresponds to an orientation of the casing on the housing outside any position assumed by the casing during pivoting of the handle through the predetermined angular displacement about the one axis. Thus the casing can be installed on the housing in the predetermined angular position and then rotated out of the predetermined angular position to lock it axially on the housing.