Gonzalez gets a $12 million, two-year contract and Atkins receives a one-year deal with an option for 2011 that guarantees him $4.5 million.
The deals are pending physicals, according to the people, who spoke separately on condition of anonymity because the contracts had not been completed as of Thursday afternoon.
Atkins, who turned 30 on Saturday, has spent his entire seven-year major league career with the Rockies. He became a free agent last weekend when Colorado failed to offer a 2010 contract.
Atkins slumped to a .226 average with nine homers and 48 RBIs last season after hitting .286 with 21 homers and 99 RBIs in 2008. Atkins, who made $7.05 million this year, lost the third base job to Ian Stewart by the end of the season.
Atkins had a career-high 29 homers and 120 RBIs in 2006, when he was fourth in the NL with a .329 average. He batted .301 with 25 homers and 111 RBIs the following year.
His deal calls for a $4 million salary next year and includes an $8.5 million club option for 2011 with a $500,000 buyout. There are additional performance bonuses.
Atkins played 89 games at first base over the past two seasons and his experience at both corner infield spots makes him a good fit for Baltimore. Longtime third baseman Melvin Mora is a free agent, and the Orioles traded first baseman Aubrey Huff to Detroit in August.
Gonzalez, a 31-year-old left-hander, figures to get an opportunity to become Baltimore's closer. He was 5-4 with a 2.42 ERA and 10 saves last season for Atlanta and has 54 saves in seven major league seasons, including a career-high 24 with Pittsburgh in 2006.
Gonzalez pitched in 80 games this year, third-most in the majors. Preceding his delivery with an unusual, rocking motion, Gonzalez struck out 90 and walked 33 in 74 1-3 innings this year.
He would get $6 million each of the next two seasons and could earn an additional $2 million in performance bonuses. He is a Type A free agent, so the Braves would receive two draft picks as compensation for losing him.
The Orioles traded closer George Sherrill to the Los Angeles Dodgers on July 30. Other potential closers in Baltimore are Koji Uehara and Jim Johnson, who took over for Sherrill last season and finished with 10 saves.
AP Sports Writer Mike Fitzpatrick contributed to this report.