It is the first move of consequence by the new Angels front office headed by general manager Jerry Dipoto.
Iannetta, 28, is a .235 hitter in six seasons in Colorado. He is coming off a 2011 campaign in which he batted .238 with 14 homers and 55 runs batted in.
The number that impressed Dipoto and the Angels most is his .357 on-base percentage in 458 Major League games. Iannetta owns a .430 career slugging mark with a high of 18 home runs in 2008. Playing half of his games in Coors Field has been a benefit. Of his 63 career homers, 37 have been in the mile-high altitude.
"We checked two boxes today," Dipoto said, referring to acquiring a No. 1 receiver and a player who can lift the team's dismal on-base percentage. "It starts to fill in some of the holes.
"We wanted to improve our catching depth and our on-base percentage. It's not often you can get a catcher who can help you in that department, getting on base.
"Chris is a solid defender. He's improved every year. I just talked to him, and he's very excited about the opportunity to work with [Angels manager] Mike Scioscia. He's known as a catching mentor."
Having dealt their regular catcher, the Rockies promptly turned their attention to free-agent Ramon Hernandez, who spent the past three seasons in Cincinnati after playing for the Athletics, Padres and Orioles.
Iannetta, in a conference call an hour after learning of the trade, said he was "beginning to get comfortable with it" after spending his entire career in the Colorado organization. He feels the Angels are getting a catcher who is coming into his own after spending six Major League seasons trying to master the most difficult position on the field.
"There are so many things that go into catching that the offense -- no matter how much you're working on it -- becomes secondary," Iannetta said. "You're trying to be the best defensive catcher you can be. From an offensive standpoint, turning the lineup over, anything you can add is a bonus.
"This past season, getting a chance to play every day made me realize a lot of things about baseball. It's easier to play every day than to sit on the bench. I learned mental patience, to trust what you put into it. After I became more confident, it really started to show in the second half."
Iannetta said he was "excited" to join an organization with a winning history and is looking forward to catching the Angels' talented trio of Jered Weaver, Dan Haren and Ervin Santana.
"I've faced all those guys and have a ton of respect for them," Iannetta said. "All three of those guys can be in Cy Young [Award] contention."
Making a career-high 105 starts in 2011 for the Rockies, Iannetta threw out 26 percent of runners attempting to steal. Only three Major League receivers catching 95 or more games had a higher percentage.
"He's a leader behind the plate," Dipoto said. "Pitchers like to throw to the guy. He has a presence. He fits in the lineup, in the clubhouse. This guy has skills."
With the Winter Meetings running Dec. 5-8 in Dallas, Dipoto said he plans to be busy exploring ways to improve both the offense and the depth in the pitching staff.
"We're interested in the best players in the world that are out there," he said.
Chatwood, a native Southern Californian who attended high school in Redlands, was the team's top Draft pick in 2008. He rose swiftly through the farm system with a mid-90s fastball and a big curveball, reaching the Majors in 2011 at 21. He'll be 22 in two weeks.
Dealing Chatwood, one of the premier starting prospects in the organization, was not an easy decision, Dipoto said.
"Trades are never easy," he said. "But catching is never easy to come by. Getting a guy who's in the top half in offensive performance at the position is hard. It's difficult to give up Tyler, but it's a reflection of how hard it is to come up with catching in the big leagues, more than a reflection of Tyler Chatwood."
An early-season injury to Joel Pineiro and Scott Kazmir making only one start created holes in the rotation, bringing Chatwood to Anaheim quicker than he or anyone in the organization had anticipated. He made 27 appearances, 25 as a starter.
Command was Chatwood's biggest challenge as he went 6-11 with a 4.75 ERA for the Angels before returning to Triple-A Salt Lake for four starts.
In 142 innings, Chatwood issued 71 walks while striking out 74 batters.
In the National League, Chatwood -- an excellent athlete who could have been drafted as a center fielder -- will be able to use his impressive hitting abilities.
While offense was clearly a factor in the Angels' decision to pursue Iannetta, he is considered a solid, cerebral defender well regarded for his ability to call games.
The Angels didn't get much offense last season from their catchers. Jeff Mathis batted .174, Bobby Wilson .189 and Hank Conger .204. Conger, who turns 24 in January, is considered the team's catcher of the future but needs to make some refinements defensively.
"Right now we have four Major League catchers on the roster," Dipoto said. "Like pitching, you can't have too much catching. It's a long way to Opening Day."
A fourth-round pick out of the University of North Carolina in 2004, Iannetta hit .264 in 104 games in 2008, but he struggled the following two years and was demoted to Triple-A Colorado Springs each season. He regained his footing and was a solid performer throughout 2011.
Mathis and Wilson are candidates to be traded. Mathis, who will be eligible for free agency after the 2012 season, shared the catching job with Mike Napoli for four seasons and excelled defensively, ranking among the best in the game with the glove.
Wilson is a solid, intelligent receiver and a contact hitter with developing power.
Having acquired Iannetta, the Angels also have the option of non-tendering Mathis in his final year as an arbitration-eligible player.
"We'll cross that bridge when we get there," Dipoto said.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.