Barrett – a two-time World Rugby Player of the Year – has penned a four-year contract to keep him in New Zealand through to the end of the 2023 World Cup.
But the 28-year-old and 73-cap New Zealand international will represent the Blues at club level from 2020, leaving Super Rugby rivals the Hurricanes, where he broke through in 2011.
The complex new contract will see first five-eighth Barrett join the Blues midway through the 2020 season, however, as he takes an extended break from rugby at the end of this year.