Abstract: An anti-rotation device prevents right-hand rotation of a tubing string within a stationary well casing. The device includes a tubular housing connected inline with the tubing string. A fixed jaw configured for gripping the well casing projects outwardly from the housing. A pair of collars free to rotate about the housing support two floating jaws, which are also configured for gripping the well casing. The floating jaws rotate about the housing between a free position in which the floating jaws are positioned adjacent the fixed jaw and the overall diameter of the device is less than the diameter of the well casing and an engaged position with the floating jaws and the fixed jaws situated on opposing sides of the housing and the overall diameter of the device is greater than the diameter of the well casing.