A surgical instrument comprising an elongate shaft assembly that defines a shaft axis. A surgical end effector is pivotally coupled to the elongate shaft assembly for selective articulation relative to the elongate shaft assembly about an articulation axis that is transverse to the shaft axis. An articulation cable is coupled to the surgical end effector at a point of attachment and is journaled on a proximal pulley that is supported on the elongate shaft assembly. The proximal pulley defines a proximal pulley axis that is located a tension distance from the point of attachment. An articulation driver is coupled to the articulation cable for selectively causing the articulation cable to rotate about the proximal pulley in first and second articulation directions. An adjustable tensioning assembly interfaces with the proximal pulley to selectively adjust the tensioning distance.