No monetary figure was disclosed, but The Denver Post reported Iannetta will be paid $8.3 million with a $5 million club option for a fourth season.
Iannetta, 26, experienced a poor 2009 with a .228 batting average, 16 home runs and 52 RBI. He lost his starting job late in the season to free agent Yorvit Torrealba.
"The season didn't really go the way I wanted it to, but in the little bit of time I got in September, I could see a lot of the work was beginning to pay off," the 2004 fourth-round pick said Friday on the Rockies' Web site. "Hitting for power is something I know I can do and have done."
Colorado added it is still trying to re-sign Torrealba this off-season.
Copyright 2009 by United Press International.