The present invention provides a polyester resin composition comprising (A) a polyethylene terephthalate composed mainly of repeating units derived from a dicarboxylic acid containing terephthalate acid and/or an esterified derivative thereof and a diol containing ethylene glycol and/or esterified derivative thereof, and (B) an ethylene/(meth) acrylic acid copolymer and, optionally, (C) polyethylene. The polyethylene terephthalate contains diethylene glycol units in a ratio of 0.5 to 2.0% by weight and a cyclic trimer in an amount not greater than 0.5% by weight based on polyethylene terephthalate. The ethylene/ (meth) arcylic acid coploymer is in an amount of 0.1 to 10,000 ppb based on the composition. Also provided are a perform formed from the composition and a blow molded container produced therefrom.