An adjustable wrench having locked and unlocked conditions is provided. The wrench includes a wrench body including a fixed jaw, and a movable jaw slidably mounted on the wrench body. The wrench body includes first and second contact walls, the second contact wall having a wall cam surface. The wrench also includes an adjuster assembly including a worm gear on the body between the contact walls and threadedly engaged with the movable jaw for moving the movable jaw toward and away from the fixed jaw, and a locking disc disposed between the worm gear and the second contact wall and having a disc cam surface engagable with the wall cam surface of the second contact wall. The locking disc is movable by a user's finger between the locked and unlocked conditions, wherein the disc cam surface engages the wall cam surface in the locked condition for wedging the adjuster assembly and the locking disc between the first and second contact walls to substantially prevent rotation of the worm gear and movement of the movable jaw, the locking disc in the unlocked condition releasing the disc cam surface from engagement with the wall cam surface so that the worm gear is free to rotate.