CBSSports.com is reporting that it is a one-year deal.
The hope for the Mariners is that Hart will bat behind recently signed second baseman Robinson Cano, who is expected to be introduced in Seattle on Thursday after signing a 10-year, $240 million pact last week.
Hart missed all of the 2013 campaign for the Milwaukee Brewers with a right knee injury. However, he hit .270/.334/.507 with 35 doubles, 30 homers and 83 RBI over 149 games in 2012.
Although Hart has spent the majority of his career in the outfield, he did play 103 games at first base two years ago.
The 31-year-old Kentucky native had spent his entire career in Milwaukee after being selected by the Brewers in the 11th round of the 2000 amateur draft.
Over 945 games, the two-time All-Star has batted .276 with 154 homers, 508 RBI and 83 stolen bases.
12/11 15:03:21 ET