The invitation was made in a letter congratulating him on his election victory, dated 9 November 2016.
Arlene Foster and Martin McGuinness told Donald Trump that he could be "assured of a warm welcome".
In November, a statement was released in which Mrs Foster and Mr McGuinness congratulated the president-elect.
But that statement did not include their invitation to President Trump.
In a joint letter released after the story appeared in The Impartial Reporter, the former first and deputy first ministers described Northern Ireland as a small region with "strong historical, economic and political ties to the United States".
The letter says Northern Ireland has "become a magnet for American companies looking for a European base" and they tell Mr Trump: "Our relationship has proved mutually beneficial for both your great country and our small but dynamic region."
Mrs Foster and Mr McGuinness then wish Mr Trump every success in his new role and extend an invitation to visit.
The former first and deputy first ministers invited US President Donald Trump to Northern Ireland when he was elected in November.