Ian Thorpe is in rehab after being found disoriented at 3am on a combination of antidepressants and medication for a shoulder injury.
His admission to hospital comes days after his management denied the swimming great was in rehab battling depression and alcohol abuse.
Thorpe was taken for a medical assessment on Monday to Bankstown hospital which wouldn't release him unless he went into rehab.
"He is in rehab for depression," his manager James Erskine told AAP.
Police were called to a street in Panania in Sydney's south on Monday morning after a resident reportedly spotted a man trying to break into a van.
But Mr Erskine said the five-time Olympic gold medallist had thought he was sitting in his friend's car.
"The owner of the car basically called the police and the police came," he said.
"They realised it was Ian Thorpe.
"They realised he was disoriented."
Mr Erskine said Thorpe, 31, had been taking antidepressants and medication for his shoulder.
"He hadn't had a drink," he said.
"He had zero alcohol in him."
A NSW police spokeswoman said no further action would be taken.
Last week, Thorpe's management denied reports the star had endured the latest round of a decade-long battle with depression and alcohol abuse.
It was reported he left rehab on Friday morning but his management company SEL said the former world champion had undergone shoulder surgery.
"Ian is not in rehab," an SEL representative said at the time.
"Ian was in hospital for an operation on his shoulder and is pleased to let his friends and fans know that he is now out of hospital and on the mend."
However, friends claimed Thorpe had struggled to adjust to life after a failed comeback for the London Olympics.
Thorpe released an autobiography last year in which he revealed his battle with depression.
- Readers seeking support and information about depression can contact Lifeline on 13 11 14 or Beyond Blue on 1300 22 46 36.