In the title mol-ecule, C(15)H(12)O(3), the two six-membered and one five-membered fused-ring system is almost planar and the CH(2)C(=O)OH residue is essentially orthogonal to it. In the crystal structure, centrosymmetric dimers are formed via the carboxylic acid {⋯O=C-O-H}(2) synthon.