However, Mr Mallon who first took the seat in 1986, has lost about 2,000 votes on his 1997 majority.
In 1997, his majority over the Ulster Unionist's Party Danny Kennedy was 4,889.
In his victory speech, Mr Mallon said: "I have been proud and privileged to represent all of the people of this constituency.
"It has been something that as long as I live I will remember with pride."
He said people in Northern Ireland were moving towards reconciliation and towards living together.
The deputy first minister said that remained his main objective.
Newry and Armagh result
In 1997, Sinn Fein was more than 11,000 votes adrift of Mr Mallon.