Commemorative services were held around the country on Friday, including at the Australian Vietnam Forces National Memorial in Canberra.
Prime Minister Anthony Albanese, who attended an event in Ipswich, said Australians respected the valour, integrity and character of those who served in Vietnam.
"Let us say to every one of our Vietnam veterans, today and every day, we honour you, we thank you and we are sorry that as a nation it took us so long for us as a nation to do so."
He said the nation had matured enough to embrace the truth that "we can disagree with a war without that diminishing the respect we feel for every man and woman who puts on our uniform and serves in our name".
"Respect for your valour, your integrity and your character.
"Respect for the truth that you have all paid a price – a price that some are still paying.
"Respect for the fact that you live with the memory of mates who never came back, and memories of all that you lived through."
Veterans' Affairs Minister Matt Keogh told the Canberra event the experience of the Vietnam conflict reflected Australia's character.
"It's about knowing no matter how dire the circumstances, your mates will always have your back."
Governor-General David Hurley paid his respects alongside Vietnamese Ambassador to Australia Nguyen Tat Thanh.
In Sydney, veterans minister David Harris was at the Cenotaph in the CBD alongside RSL NSW President and Vietnam veteran Ray James.
"For those of us who are still here today, I say we must continue to honour the dead but fight like hell for the living as we support our fellow veterans of all conflicts, and connect them with the mateship, camaraderie, and services they need," Mr James said.
About 60,000 Australians served in Vietnam, with more than 3000 wounded and 523 killed. Some 15,000 were conscripted under the National Service Scheme.
Upon returning home, veterans experienced hostility from the community over their involvement in an unpopular conflict, including being spat on and having paint thrown on them during parades.
Opposition Leader Peter Dutton, together with defence spokesman Andrew Hastie and veterans' affairs spokesman Barnaby Joyce, said the war was a polarising conflict.
"At the time, public opinion often failed to draw a distinction between the politics of war and the people who fought in it," they said in a joint statement.
"In the decades since the Vietnam War, we have come to acknowledge our nation's historical mistreatment of many who returned.
"And we have come to tell stories of the endeavours, valour and sacrifice of Australians who served in Vietnam - to see beyond the politics and rightfully honour the people, their character and their deeds."
It is estimated more than 35,000 Australian Vietnam veterans are still living, with most aged 70 or older.
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