The Underbelly: A Tale of Two Cities star was arrested on Friday (06Apr12) on charges of obstruction and trespass.
He was released on bail from a Miami Dade jail late on Saturday (07Apr12).
Reports suggest the actor was drunk and abusive when he was arrested at a bar he refused to leave.
The run-in with the law is the latest in a series of headline-grabbing missteps that have blighted Newton's career in recent years.
The actor, who has a history of mental illness, was in Florida for appointments with medical experts, according to his attorney. Following his release from jail he was placed in the care of ""health professionals"".
The star's problems began to unfold in 2010 after he allegedly attacked ex-fiancee Rachael Taylor during a row on a vacation in Italy. The Transformers actress obtained a restraining order against him, prompting a major Australian TV network to drop him as the host of a talent show series.
Last month (Mar12), officials in Sydney ordered the actor to return to Australia to face allegations he assaulted a taxi driver in December (11).
He is expected to face assault charges at a hearing on 10 April (12) at Sydney's Downing Centre Local Court.