A wrench with a rotatable head comprises a handle and a head, which are connected via a first and a second ends. The first end includes an upper and a lower lugs. A first toothed hole is formed in the upper lug; a hole is formed in the lower lug. A second toothed hole is formed in the second end. The second end is inserted between the upper and lower lugs and the second toothed hole is located between the first toothed hole and the hole. A toothed pillar is movably engaged in the toothed holes. When in the engagement position, the toothed pillar is engaged with the first and second toothed holes to fix the head and the handle. When in the disengagement position, the toothed pillar is disengaged from the teeth of the first toothed hole but still engaged with the teeth of the second toothed hole, so that the head and handle are rotatable with respect to each other.