Phoebe was born in Sydney, Australia. When she was four, Tonkin attended several dance courses, classical ballet, hip hop, contemporary dance and tap dance. At the age of twelve, she began courses at the Australian Theatre for Young People (ATYP) at the Wharf Theatre. She later graduated from Queenwood for Girls in Balmoral, Newn South Wales Balmoral. Tonkin has appeared in a number of commercials which include Vauxhall Motors and Chick Management, also modeled for Girlfriend (magazine) and Teen Vogue Dolly (magazine). She has also appeared in Miles Fisher music video "Don't Let Go".
In December 2005, Tonkin was cast as the role of Cleo Sertori on the Australian children tv show H2O: Just Add Water which follows the lives of three teenage girls who turn into mermaids. Tonkin improved on her swimming abilities during the pre-production of the series. The series premiered on 7 July 2006 on Network Ten and has since gone on to be aired to a worldwide audience of more than 250 million. To promote the series she and her co-stars presented the best band award at the Nickelodeon UK Kids Choice Awardsin October 2007. In 2008, Tonkin was nominated for "Best Lead Actress in a Television Series" Australian Film Institute Awards The series ran for three seasons with the series finale airing on 16 April 2010.
Tonkin has also appeared on fellow Australian television shows Packed to the Rafters, Home and Away. In September 2010, Tonkin made her film debut starring in the Australian action ensemble film Tomorrow, When the War Began. In the film, which revolves around a group of teenagers waging a guerrilla war against an invading foreign power in their fictional hometown of Wirrawee, she played the role of the rich and uptight Fiona Maxwell. In December 2010, a sequel was announced with Tonkin expected to return.
In January 2011, Tonkin moved to Los Angeles to pursue an international acting. She was cast in March 2011 as Faye Chamberlain on supernatural drama series The Secret Circle which premiered on 15 September 2011 to over 3.5 million viewers. The series follows a group of young witches whom are a part of a secret coven. Tonkin has received acclaim from critics being referred to as the breakout star of the series; she was featured on Variety "new faces to watch" and named one of 2011's breakout stars & Phoebe Tonkin TV stars E! Online.The Secret Circle, however, had only one full season as it was cancelled on 11 May 2012. In August 2010, Tonkin was cast in the film Bait Filming took place on Australia Queensland Gold Coast and follows a group of strangers who are trapped in a supermarket after a freak tsunami with a pack of great white sharks. The film is expected to be released in Australia in September 2012. In August 2012, Tonkin was reported as being cast in the TV series The Vampire Diaries in a recurring role as Hayley, a friend of Tyler, joining her co-star from H2O: Just Add Water, Claire Holt, who portrays Rebekah Mikaelson.
Year TV/Movie Role 2006-2010 H20: Just Add Water Cleo Sertori 2009-2010 Packed the Rafters Lexi 2010 Home and Away Adrian Hall 2011-2012 The Secret Circle Faye Chamberlain 2012-2013 Vampire Diaries Hayley 2013 The Originals Hayley
Year TV/Movie Role 2010 Tomorrow, When The War Began Fiona Maxwell 2012 Tomorrow, When The War Began 2 Fiona Maxwell 2012 Bait Jamie
- Phoebe was cast in the sister show of The Vampire Diaries, The Secret Circle.
- Phoebe and Claire Holt are real life best friends and worked as mermaids on a TV show together back in 2006 that was called H2O: Just Add Water .
- Phoebe's character Faye Chamberlain was considered the "Damon" of the sister show The Secret Circle.
- She has a younger sister named Abby.
- After cancelling The Secret Circle, Kevin Williamson decided to write her into one of his other shows, what brought her to The Vampire Diaries.
- Both she and Claire Holt have made there debuts on the show in a season's third episode, Phoebe in The Rager in the fourth season, Claire in The End of The Affair in the third season, and have been recurring characters from so on.
- After the CW's hit shows "Smallville" and the superhero show "Arrow" CW is in early works for a Wonder Woman show called "Amazon" which is Diana Prince's origin story before she became Wonder Woman. It's been suggested that Phoebe could take on the lead role.   Phoebe admitted she's interested in Amazon. Casting is being called for the lead role and matches Phoebe's description. 
- It was revealed that she will star on the Vampire Diaries spin-off pilot (the Originals) as Hayley. 
- Phoebe is very clumsy, she trips over things and falls. She admits she can't control her legs.
- When Phoebe decided to call and tell Claire she was coming to Atlanta, she made Claire lock herself in her trailer and be completely alone, and not tell anyone else because no one else was suppose to know yet. When she told Claire, Claire screamed, and Phoebe told her, her trailer door better be closed.
- Phoebe admitted that one of the best character's to her on the show is Rebekah, because of she's awesome, cool, funny, and sexy.
- She's friends with Alexandra Chando, who is one of Nina Dobrev's celebrity doppelgängers.
- Phoebe Tonkin and Teresa Palmer are creating a website for heath, called "Your Zen Life". 
- She is named as one of Australia's fittest woman.