The Opposition Labor Party led by Mark Latham, 43, conceded defeat after it lost traditional seats in the island state of Tasmania and key marginal seats in other parts of the country.
The ruling coalition achieved an overall swing of 2.13 percent of votes on a two-party
Exit polls predicted the ruling coalition would increase its number of seats in the 150-member House of Representatives -- from 82 seats to 87.
Labor was predicted to lose at least four seats to get 60, with the three remaining held by independents.
This makes Howard Australia's second longest serving prime minister, after Liberal Party founder Robert Menzies, who remained in office for 17 years from 1949.