The signing indicates that Oleksiak will be the Kraken's selection from the Dallas Stars, where the defenceman played his last three seasons.
It also marks Seattle's second signing of the day so far. The Kraken signed former Edmonton Oilers defenceman Adam Larsson to a four-year deal earlier today.
Oleksiak, 28, is coming off a three-year, $6.412 million deal. He scored six goals and added eight assists in 56 games during the 2020-21 season.
The Toronto native began his nine-year NHL career with the Stars after they selected him 14th overall in the 2011 NHL Entry Draft. He was traded to the Pittsburgh Penguins in December 2017, before being reacquired by Dallas via trade just over a year later.