The invention relates to a mechansim for enabling independent pitch control of airfoil blades of contra-rotating rotor assemblies. The mechanism is of particular benefit when applied to 'open rotor' gas turbine engines. The disclosed pitch change mechanism (40) for an open rotor gas turbine engine (10) comprises an engine having a first rotor assembly (20) and a second rotor assembly (30), with a plurality of airfoil blades (21, 31) circumferentially mounted on each rotor assembly and arranged in contra-rotational relationship to each other. The pitch change mechanism includes an actuator assembly (50) adapted to be secured to a non-rotating frame (12) of the engine. The actuator assembly has a first actuator (51) and a second actuator (52) with the actuator assembly being rotationally isolatable from and couplable to the first and second rotor assemblies. An actuation signal from the first or second actuator induces a corresponding desired change in pitch of the airfoil blades of the respective first or second rotor assembly independently of the pitch of the airfoil blades of the second or first rotor assembly.