"We've agreed that he will be staying with us," said Saints' chairman, Eamonn McManus. "He's had an unfortunate season with injury, but when we get him fit again it will be the Hooper of old next season."
His retention deepens the mystery of where Saints plan to play Leon Pryce, when they confirm his signing from Bradford, but McManus said that Hooper re-signing would not change their plans. Hooper, who can also play back-row, said that he had been approached by other clubs in England and Australia.
Paul Anderson has also signed a new one-year contract to stay with Saints.
Leeds have loaned their promising young loose forward Carl Ablett to the London Broncos for a month.
"We have had a number of players down at London on loan and it has been really beneficial for them," said the Rhinos' coach, Tony Smith.
The St Helens referee Steve Ganson is to take charge of the Powergen Challenge Cup final between Leeds and Hull in Cardiff on 27 August.