Kerry fought in Vietnam as a naval officer before returning to the United States in 1969 to become a prominent opponent of the war, his first foray into public life.
Later, as a US senator, he worked to mend ties between the former foes and as secretary he has now made four visits to the country where once he battled Viet Cong rebels.
He is due to leave office next week when President Barack Obama hands over power to President-elect Donald Trump, but not before Kerry's final diplomatic trek.
On Saturday, he will head to the Bay Hop river in Ca Mau province where, in February 1969 he beached his patrol boat and stormed ashore to shoot dead a Viet Cong ambusher.
More From This Section
Kerry won a Silver Star for this action, which saved the crew of his small naval Swift Boat from rocket attack.
But he came to see the war as a mistake and US tactics as counterproductive in the battle for Vietnamese hearts and minds. In 1971, after his return, he campaigned for peace.
His talks in Hanoi will also touch on tensions in the South China Sea, where Vietnam is one of several Southeast Asian nations disputing China's territorial grab.
Under Obama and Kerry, Washington has remained neutral in the overlapping disputes while insisting that all shipping must enjoy freedom of navigation in the disputed waters.
But on Tuesday Trump's nominee to replace Kerry, former oilman Rex Tillerson, said Washington should take steps to halt China's tactic of building on disputed reefs.
Trump has frequently condemned the deal as a threat to US jobs, and his November election victory had appeared to sound the death knell for the ambitious economic pact.
But Tillerson also said during this week's Senate confirmation hearing that he does not oppose TPP.
After his stopover in Vietnam, Kerry will head on to Paris for a Middle East peace conference on Sunday, then on to London and the World Economic Forum in Davos next week.