Iannetta, 32, spent the past four seasons with the Angels after being acquired by Dipoto in a trade with the Rockies in 2011. He gives Seattle an experienced catcher to take the pressure off Mike Zunino, a well-regarded 24-year-old who has struggled to hit at the Major League level and finished last season with Triple-A Tacoma.
"Chris has a very distinct skill set and really brings an added dimension," Dipoto said. "Not only stability behind the plate, where he's worked very hard to improve, but he's also a veteran with an idea when he gets into the box. He does a lot to help your lineup get longer."
Iannetta is coming off a rough 2015 season, having batted .188 with 10 homers and 34 RBIs in 92 games after getting off to a slow start with a .093 average in April. But he carries a career line of .231/.351/.405 in 10 seasons in the Majors with the Rockies and Angels and hit .252/.373/392 in 108 games in 2014. Dipoto feels last year's low average is misleading.
"Chris had a horrific year on batting average on balls in play, and usually that's indicative of just being a little unlucky," Dipoto said. "He's got good right-handed power and an excellent walk rate. He's always drawn deep at-bats and gotten on base. The other numbers all stacked up. As a result, I think Chris is good candidate for a bounceback year offensively. And regardless, he's a player that brings us stability behind the plate and has been through Major League battles."
Iannetta's .351 on-base percentage since the start of 2006 is tied for the third-best among catchers with a minimum of 3,000 plate appearances behind San Francisco's Buster Posey (.375), Toronto's Russell Martin (.352) and tied with Philadelphia's Carlos Ruiz (.351).
Iannetta said he got in some bad habits at the plate last spring that took time to overcome, but he felt he finished the season well and is looking now to show what he can do with regular playing time again.
"It's an opportunity to get back in a situation where I could play and prove this past year was just a down year and something I'm not proud of," he said from his offseason home in Rhode Island. "It really affected me. This is an opportunity to regain some confidence and go out there and show what I'm capable of doing."
Iannetta earned $5.5 million last season in the final year of a three-year, $15.5 million contract and was credited with helping mentor Angels rookie Carlos Perez, who eventually replaced him as the starting catcher in the second half.
He said he's been impressed by Zunino's improvement behind the plate and wants to help him in any way possible.
"Catching behind him when he's hitting, I've seen a lot of things I kind of felt when I was young in Colorado," Iannetta said. "I see a lot of similarities there. He's going to be a really good player. It could be this year when he figures it out and takes off or it could be next year, but it's going to happen. He's too good and too talented and works too hard for it not to happen. I look forward to being around him. I really do. And if I can help him get to the next level, I'd love to be able to do that."
Dipoto indicated Zunino's development remains a critical part of the Mariners' plans and that no catcher plays 162 games a year.
"Whether it's a time share or backup, Mike will be in position to win some of that playing time," Dipoto said. "He's still a young guy, and we need to get him back on track."
Zunino, the third overall pick in the 2012 Draft, is a strong defender and handles pitchers well, but he hit just .174 with 11 homers in 112 games in 2015.
Dipoto has made four trades involving 16 players in the past three weeks and also re-signed Mariners free-agent outfielder Franklin Gutierrez, but Iannetta represents his first free-agent pickup from another club.
Hicks, a fourth-round selection in the 2011 Draft, joins former Virginia teammate Danny Hultzen on the DFA list. The Mariners designated Hultzen for assignment on Friday. The club has 10 days to trade, release or outright both players to the Minors.