Heading overseas allows Childress to make more money than he could have as a restricted free agent in the United States. The Hawks had the right to match an offer from another NBA team, but not from an international club.
Agent Jim Tanner said Wednesday the three-year deal was worth about $20 million after taxes. The money is guaranteed, and Childress can opt out of the contract after each year.
The deal is the most lucrative current contract in European basketball and the biggest in Euroleague history, according to the Atlanta Journal-Constitution, which first reported the signing. It follows the decision by top prep prospect Brandon Jennings to sign with an Italian club team rather than play a season at Arizona.
The newspaper reported Monday the Hawks had a deal on the table worth nearly $36 million, with a first-year salary in excess of the midlevel exception of $5.6 million.
"I've talked to a few guys, and it could become a trend," Childress said on a conference call about other Americans following his lead. "I'm not so sure it won't. It's different. We thought out of the box a little on this one."
The 6-foot-8, 210-pound guard/forward averaged 11.8 points and 4.9 rebounds as the Hawks' top reserve last season. He averaged 11.1 points and 5.6 rebounds in four years with Atlanta about being drafted sixth overall in 2004 out of Stanford.
Childress said he intended to re-sign with the Hawks, who made the playoffs for the first time since 1999 and pushed the eventual champion Celtics to seven games in the first round. But when he felt the team didn't show a sense of urgency in making a deal, he looked elsewhere.
Atlanta general manager Rick Sund said that while he believes the Hawks made a proposal that was competitive within the NBA, it would have been fiscally irresponsible to try to match Olympiacos. Sund wouldn't reveal the exact numbers of Atlanta's offer. But he said it exceeded the salary cap's midlevel exception, which is more than $5.5 million, and would have made Childress the team's fourth highest paid player.
"Obviously I'm not happy with it because I wanted him on my team. I wish things would have turned out different, but it's his decision at the end of the day," Hawks center Al Horford said. "I'm disappointed about it because he's one of the guys that I really liked to play with, but we have to be able to bounce back and try to sign the other Josh [free agent Josh Smith]."
Olympiacos initiated the contact, said Lon Babby, another of Childress' agents. With the strength of the euro against the dollar, Babby believes international clubs now have the resources to pursue high-level American players -- and other restricted free agents may reciprocate the interest because it creates leverage they lack within the NBA.
"The path to globalization that the NBA has paved for years now appears to travel in both directions," Babby said.
International players have spurned the NBA for lucrative offers back home in the past, but Americans of Childress' caliber have not done so in the prime of their careers.
"I think it's always going to happen when you get a player that's pretty solid over here and then they get offered more money, it's hard to pass up," Toronto Raptors star Chris Bosh said. "Especially guys in the midlevel range when they can go over to Europe and probably make a little bit more money, it's always a better situation for them."
Phoenix Suns chairman Jerry Colangelo, the managing director for USA Basketball, expected the trend to be limited to players like Childress who are solid contributors but not big stars.
"It's an opportunity for players who fall into that kind of a niche or category to have an option available to them," Colangelo said. "So it's a players' market."
After an initial meeting with Olympiacos officials in Las Vegas, Childress traveled to Athens on Sunday and liked what he saw. He said he feels confident he can adapt to a different culture.
The Hawks would retain Childress' NBA rights, and he would remain a restricted free agent, if they make a qualifying offer each year, Babby said. That would count against their salary cap, though. If they don't, he'd become an unrestricted free agent.
Olympiacos finished runner-up in the Greek basketball league last year, behind rival Panathinaikos. It has boosted its roster with summer transfers -- including Greece star Theodoros Papaloukas, who was signed from CSKA Moscow.
Information from The Associated Press was used in this report.