The president arrived at the Australian War Memorial in Canberra shortly after 9am (AEDT) on Thursday.
He was welcomed by Governor-General Quentin Bryce, Prime Minister Julia Gillard, Veteran Affairs Minister Warren Snowden and memorial council chairman Peter Cosgrove.
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Mr Obama entered the war memorial under the cover of a marquee after emerging from his bomb-proof Cadillac.
He walked to the Hall of Memory where he laid a wreath at the Tomb of the Unknown Soldier.
On a walk past the Wall of Remembrance, which contains the names of more than 100,000 Australians killed in action, the president paused at two panels.
The first was for HMAS Sydney, sunk with all hands in Australia's worst naval disaster in 1941.
The second was for more than 30 Australian airmen who lost their lives serving with the US Armed Air Force in World War II.
