A width adjustable worktable includes a worktable body, an extension member movable relative to the body, a first guide rod connected to the extension member and a control set rotatably mounted in the extension member. The control set is operable to move the first guide rod between a locking position, where the first guide rod is prevented from moving relative to the worktable body, and an adjustable unlocking position, where the first guide rod is unlocked and movable relative to the worktable body for allowing the user to move the extension member carried by the first guide rod to adjust the width of the worktable.