McCann's third hit, a bases-loaded single, scored Nate McLouth and gave Atlanta a 3-2 lead in the fifth inning. Garret Anderson followed with a run-scoring walk.
Hanson (1-0) struggled in his second major league start but managed to limit the Orioles to two runs despite yielding nine hits and five walks in 5 2-3 innings.
Hanson departed with the bases loaded but Peter Moylan struck out Adam Jones to end the threat. Eric O'Flaherty, Rafael Soriano and Mike Gonzalez each worked a scoreless inning to close it out.
Atlanta pushed across a run in the seventh and two more in the eighth to break it open. Jeff Francoeur made it 5-2 with an RBI single. Martin Prado hit his third homer and McCann singled in a run in the eighth.
It was McCann's third career four-hit game and first since Aug. 27, 2006.
Jason Berken (1-3) allowed four runs and eight hits in 4 1-3 innings for Baltimore, which has lost 10 of 12.
The Orioles continued to have difficulty scoring. They left 13 on base and have scored just 19 runs in the past 11 games.
After manager Dave Trembley called a team meeting to encourage them, they came out aggressively. Trailing 2-0 in the bottom of the first, Brian Roberts doubled on Hanson's first pitch, stole third and scored on Jones' grounder.
Aubrey Huff added an RBI single in the third for Baltimore.
Yunel Escobar hit a two-run shot in the first to give Atlanta a 2-0 lead.
NOTES: Hanson allowed six earned runs in six innings against Milwaukee in his first start Sunday. ... Atlanta 1B Casey Kotchman, who has been on the 15-day disabled list since June 1 with a strained right calf, will start a rehab assignment at Triple-A Gwinnett on Saturday. ... Chipper Jones, who was Atlanta's DH, was hitless for the third straight game for the first time since July 7-9, 2008. ... Orioles RF Nick Markakis recorded his AL-leading sixth assist. ... Baltimore's Luke Scott played the ninth inning at 1B for the first time in his career.
Atlanta Braves starter Tommy Hanson delivers a pitch against the Baltimore Orioles during the first inning of a baseball game, Friday, June 12, 2009, in Baltimore. (AP Photo/Nick Wass)
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