In a valve operating system for an internal combustion engine provided with valve operating characteristics changing member capable of changing operating characteristics of an engine valve, the valve operating characteristics changing member includes a connection operating member which is provided in common at a drive rocker arm and both free rocker arms to be capable of switching an alternative connecting state of the drive rocker arm to both the free rocker arms and a release state of connection of the drive rocker arms to both the free rocker arms. Thus, the operating characteristics of the engine valve can be reliably switched with favorable responsiveness.