The Mariners will introduce Servais, 48, at a news conference on Monday.
"I am excited and grateful for the opportunity to manage the Seattle Mariners," Servais told MLB.com. "It has long been my goal to manage a big league team and while I took a slightly different path than many, I am confident in my ability to lead.
"We have a terrific core of players and I'm looking forward to bringing in a coaching staff that will help me establish a winning culture here as we work toward putting a championship-caliber team on the field for the fans of the Northwest."
Servais, Red Sox special assistant Jason Varitek and minor league manager Phil Nevin were among the finalists for the job, according to multiple media reports. He will replace Lloyd McClendon, who was fired earlier this month after two seasons as Seattle's manager.
Mariners general manager Jerry Dipoto and Servais shared a working relationship with the Angels, where Dipoto was GM and Servais oversaw scouting and player development.
Dipoto came to Seattle after leaving behind a rocky relationship with the Angels and manager Mike Scioscia over the summer. He and Servais shared a similar organizational philosophy in the Angels organization, so a re-teaming of the two wasn't a major surprise.
The Mariners haven't made the postseason since 2001, the longest playoff drought by any Major League Baseball team. The only team in any of the four major sports with a longer drought is the Bills, who last made the postseason in 1999.
Servais was the Angels' assistant GM for four seasons. Before that, he was the Texas Rangers' senior director of player development from 2006-2011. Servais was a catcher for four teams over 11 major league seasons and he also was a member of Team USA that won gold in the 1988 Olympic Games.
Information from ESPN Stats & Information was included in this report.