The deal is still pending a physical that is expected to take place later this week, The Associated Press reported.
Bloomquist would be the Mariners' first offseason signing and provides them a utility player who can play both infield and outfield positions.
Bloomquist spent the past three seasons with the Arizona Diamondbacks, appearing in 225 games and hitting .289 with 36 doubles and 63 RBIs over that time. Last season with Arizona, he appeared in 48 games and had 139 at-bats.
Bloomquist spent the first seven seasons of his career with the Mariners. His high point came in 2006 when Bloomquist appeared in 102 games for Seattle. He spent the 2009-10 seasons with Kansas City and Cincinnati before joining the Diamondbacks.
Information from The Associated Press was used in this report.