The love story landed the ultimate honour, the Best Film nod, as well as trophies for Best Original Screenplay and Best Direction.
The movie's writer/director, Warwick Thornton, accepted the awards, telling the crowd in Melbourne, Australia, "It's hard work, it's b**ody hard work, there is no mucking around. Be careful what you write, you might just have to direct it."
The child stars of the movie, Marissa Gibson and Rowan McNamara, also shared the Young Actor accolade - and Thornton heaped praise on them, adding: "We put Marissa and Rowan into these lights and part of the deal is to look after them, whatever they want to do, until they know what they want to do and they can separate themselves from us."
Anthony LaPaglia won the Best Actor award for his role in Balibo, a drama about the death of an Australian journalist. The movie's co-writers David Williamson and Robert Connolly won the film a further honour, Best Adapted Screenplay.
Despite being honoured for six awards, Baz Luhrmann's epic Australia only won the one, for highest grossing film. It garnered $211 million (£132 million) at the worldwide box office.
Gangster drama Underbelly: A Tale of Two Cities took home three awards including Best Television Screenplay, and Rachel Griffiths landed the Best Supporting Actress for her role in Beautiful Kate.
Austrian filmmaker Michael Haneke has walked away with the top honor at this year's Cannes Film Festival for his drama The White Ribbon.
The film -- about residents in a small German town riddled with tragedy as World War I approaches -- was awarded with the Palme d'Or (Golden Palm) at the annual prize-giving ceremony in the French Riviera on Sunday.
Quentin Tarantino's war film Inglourious Basterds also triumphed, with Christoph Waltz winning in the Best Actor category for his role as a Colonel Hans Landain.
Meanwhile, English/French star Charlotte Gainsbourg won the Best Actress statue for her role in Danish director Lars von Trier's drama Antichrist.
Veteran French filmmaker Alain Resnais, 86, was also awarded a special prize for his half-century career. Resnais delighted critics with Les Herbes Folles (Wild Grasses), a romantic comedy starring Sabine Azema and Andre Dussolier and the director's his first movie to compete at the festival in almost 30 years.
The jury at the 62nd Cannes Film Festival was headed by French actress Isabelle Huppert.
The main list of winners is as follows:
Palme d'Or (Golden Palm) - The White Ribbon by Michael Haneke (Austria)
Grand Prize - The Prophet by Jacques Audiard (France)
Jury Prize - Fish Tank by Andrea Arnold (Britain) and Thirst by Park Chan-wook (South Korea)
Special Prize - Alain Resnais
Best Director - Brillante Mendoza, Kinatay (The Philippines)
Best Actor - Christoph Waltz, Inglourious Basterds (United States)
Best Actress - Charlotte Gainsbourg, Antichrist (Denmark)
Best Screenplay - Feng Mei, Spring Fever (China)
Camera d'Or (first-time director) - Samson and Delilah by Warwick Thornton (Australia)
Best short film - Arena by Joao Salaviza (Portugal)
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