A bicycle rim brake is basically provided with a first brake arm and a hydraulic actuation device. The first brake arm includes a first coupling portion configured to pivot about a first pivot axis, a first actuated portion and a first mounting portion. The first mounting portion is configured to mount a first friction member and extends from the first coupling portion. The hydraulic actuation device is operatively coupled to the first actuated portion of the first brake arm. The hydraulic actuation device includes a cylinder housing defining a hydraulic chamber, a first piston movably disposed in the hydraulic chamber of the cylinder housing, and a first sealing member provided on the cylinder housing so as to at least partially support the first piston in the hydraulic chamber.