The city Department of Correction said in a statement at 5:15 p.m. that he was no longer on Rikers Island. He was released into custody of the security company that will be monitoring his house arrest.
Strauss-Kahn, charged with sexually assaulting a maid at a New York City hotel, was supposed to move to Bristol Plaza on East 65th Street, but after neighbors objected, his attorneys found him housing in lower Manhattan.
The onetime potential French presidential contender has spent nearly a week in police custody and then jail.
A judge on Thursday agreed to free the 62-year-old - provided he's confined to a New York apartment, under armed guard and electronic monitoring.
Supreme Court Justice Michael J. Obus said the conditions played a major role in his decision to allow bail, but he warned Strauss-Kahn he might reconsider "if there is the slightest problem with your compliance."
Prosecutors announced that Strauss-Kahn had been indicted on charges including attempted rape and a criminal sex act.
"The proof against him is substantial. It is continuing to grow every day as the investigation continues," Manhattan assistant district attorney John "Artie" McConnell told the judge.
Prosecutors got help from an unlikely source - the same former madam who outed former Gov. Eliot Spitzer as Client No. 9. Kristen Davis said Strauss-Kahn was also a client, but he didn't have a good reputation.
"A girl came back afterward and said that he was aggressive and rough and that she didn't want to see him again if he ever called," she said.
The Associated Press contributed to this story.