GPT head of office and logistics Matthew Faddy said the new building would be a feature in Parramatta's CBD transformation.
QBE Australia and New Zealand chief operating officer Renée Roberts said the move would be a "significant one" for the insurer.
"It will bring together our existing Parramatta-based teams with those currently located at Sydney Olympic Park, into one purpose-built, modern and flexible workspace," Ms Roberts said.
Construction is yet to begin on the Smith Street building, which is GPT's first move in the Burgeoning Parramatta office market.