Assange spoke outside of the court building after his release and told supporters he would pursue his efforts to bring government secrets to light.
"It's great to smell the fresh air of London again," he said. "I hope to continue my work."
Prosecutors sought to keep him behind bars, arguing there was a risk he would flee.
Assange faces charges in Sweden including rape and molestation after two separate women said he had sex with them without their consent.
The judge said that Assange must abide by strict bail conditions as he fights extradition to Sweden. Assange must surrender his passport, reside at a friend's address in the UK, report to police on a daily basis and observe two four-hour curfews each day.
Assange will be staying at Ellingham Hall, a 10-bedroom mansion about 120 miles northeast of central London that belongs to Vaughan Smith, a WikiLeaks supporter and founder of London's Frontline Club for journalists.
Some Assange supporters suspect the extradition request has been motivated by WikiLeaks' decision last month to begin publishing a trove of 250,000 secret U.S. diplomatic cables, something Swedish officials have denied.
Assange's next court appearance was set for Jan. 11, ahead of a full hearing on Feb. 7 and 8.
The Associated Press contributed to this report.