A firearm accessory mount includes a main part with a rail receiving portion extending in a first direction that can receive a firearm mount rail, and includes a holding part with a rail engaging portion. The holding part is movable relative to the main part so that the rail engaging portion moves approximately parallel to a second direction forming an angle to the first direction. An adjusting portion positionally adjusts the rail engaging portion with respect to the main part, approximately parallel to a third direction transverse to each of the first and second directions. A manually operable member is operatively coupled to the holding part so that the holding part is moved approximately parallel to the second direction in response to movement of the member.