Thermoplastic randomly branched copolyester-carbonate resin containing from about 40 mole percent to about 90 mole percent ester bonds which is particularly suited for blow molding operations. This branched copolyester-carbonate resin is obtained by reacting a carbonate precursor, at least one dihydric phenol, at least one ester forming reactive derivative of a difunctional carboxylic acid, and a polyfunctional aromatic branching agent.