In one general aspect, various embodiments are directed to an ultrasonic surgical instrument that has an ultrasonic blade that protrudes from an ultrasonic transducer assembly. In some embodiments, the ultrasonic blade coaxially extends through a rotatable tissue cutting blade that is rotatably supported by a housing that supports the ultrasonic transducer assembly. In other embodiments, the ultrasonic blade and the tissue cutting blade are both selectively rotatable relative to the housing. In yet other embodiments, the tissue cutting blade and the ultrasonic blade are supported relative to each other in separate sheaths attached to the housing.