Newton was born in Melbourne in 1977, and is the son of television personalities Bert and Patti Newton, brother of Lauren Newton, and brother-in-law of gold-medal Swimmer Matt Welsh. His father Bert is an icon in Australia media as an award-winning entertainer and radio, theatre and television personality/presenter and an Australian Logie Hall of Fame inductee and quadruple Gold Logie winner. Newton was educated at Xavier College and the National Institute of Dramatic Art (NIDA), where he graduated with a degree in Acting in 1998.

Newton has performed in Australia and abroad on stage, television and movies. In 1988, he starred in Sugar and Spice, a children's television series. In 1992, he starred in Late For School, a drama series that aired briefly on Channel Ten. Over the next few years, Newton had guest roles in various shows. In 2000, he starred alongside Pia Miranda in the film adaptation of the teen novel Looking for Alibrandi. In 2001 he appeared in the Australian/American science fiction show Farscape as the character Jothee, and as the vampire Armand in Queen of the Damned (in 2002).

In 2002, Newton was nominated for a Logie Award for his role in the television series Changi.

In 2004, Newton directed, wrote and starred in his first feature film, Right Here Right Now. The film was produced with private funding. In 2005, Newton starred in The Surgeon, which aired on Channel Ten.

In 2006, Newton appeared on the New Year's Eve 2006 episode of The Big Night In with John Foreman on Network Ten in which he engaged in simulated sex acts and other suggestive activity as well as bad language. The Daily Telegraph reported his antics and the station received criticism from outraged viewers who complained the show was "sub-standard coverage" and "the worst ever".

In July 2007, Newton was successful in having the conviction overturned. Solicitor Chris Murphy tendered a letter from Dr Robert Hampshire, Newton's Psychiatrist, which outlined his depressive illness and stated he was unlikely to reoffend. Judge Joseph Moore said, "It does not in any way lead the court to give special consideration to his case because he is a person of high profile", referring to Newton's Celebrity status; and, "The way in which he has been given particular media attention has acted as a considerable measure of punishment."

Newton wrote, directed and starred in the feature Three Blind Mice, which made its international premiere at the Toronto International Film Festival and won the Critics Prize at the 2008 London Film Festival.

In December 2009, Newton made headlines again after complaining about his hotel room in Mildura, Victoria.

In August 2010 following two domestic violence incidents involving girlfriend Rachael Taylor at a hotel in Rome, where Newton allegedly "punched Taylor in the face before being sedated by ambulance officers." It was reported that Taylor suffered concussion after she hit her head on the hotel's marble floor, and a sprained jaw after the alleged attack. Taylor took out an Apprehended Violence Order (AVO) against Newton. The media also reported his heavy use of alcohol, cocaine, marijuana, and methamphetamine at this time.

It is alleged that Newton assaulted a 66 year old taxi driver twice in the Sydney suburb of Crows Nest on 4 December 2011. He has been charged with Common assault and appeared in court in January 2012. The matter was originally stood over to April 2012. The matter was then stood over for a further three months as Newton was facing separate charges in the United States (see below).

On 14 November 2012 both matters were dismissed, conditional upon Newton completing 50 hours of community Service, writing a letter of apology to the hotel clerk, Ariel Bory Vargas, paying $US11,500 restitution to Mr. Vargas and staying away from both him and Mr. Moe's, the bar where he was accused of trespass.

In November 2013, Newton directed and starred in an off-Broadway production of Hamlet in New York City.