A three-port valve including a casing and a movable element received in the casing. The casing includes a fluid inlet, first and second fluid outlets, a first fluid-flow passage between the fluid inlet and the first fluid outlet, and a second fluid-flow passage between the first and second fluid outlets. The movable element includes a rod, a first valve member fastened to a first end of the rod and configured to be received towards the rod in a first valve seat for closing the first fluid-flow passage, and a second valve member fastened to a second end of the rod and configured to be received towards the rod in a second valve seat of the casing for closing the second fluid-flow passage. The valve also includes at least one diaphragm spring supporting the movable element in a plane substantially perpendicular to a movement axis between first and second positions.