Abstract: A knot tying device including a sheath configured for placement over a surgical instrument. The sheath includes a proximal end portion and a distal end portion. The distal end portion is elastically reconfigurable between a straightened configuration and a hook shaped configuration. Position of the sheath on the surgical instrument is adjustable between an extended position in which the sheath extends beyond a distal tip of the surgical instrument and a retracted position in which the sheath is pulled back from the distal tip of the surgical instrument. The distal end portion is in the hook shaped configuration when the sheath is in the extended position and the distal end portion is in the straightened configuration when the sheath is in the retracted position. In exemplary embodiments, the knot tying device may include one or more magnets or one or more magnets as an integral part of a surgical instrument.