He waved to fans and others at the golf tournament, with some asking for “four more years.”
Mr Trump stopped several times to answer questions from reporters about the conflict in the Middle East and Irish unity, as well as local issues such as objections to a ballroom at his resort in Doonbeg, Co Clare, which he said they were “trying” to build despite objections.
Read more:
On Saturday, Trump responded to questions by saying he would “love to see” Ireland united, adding: “Eventually it will happen.”
He said: “I’ve always loved the people of Ireland and it just seems to me that you have Northern Ireland and you have Ireland and it seems to me that one of the natural phenomena of all time brings them together.”
“A lot of people agree. I made what I thought was a pretty ordinary comment and I got so much support for it.”
Trump said he would “say nothing” about Scottish independence, saying he would “save it for another day”.
When asked about the diplomatic row caused by his comments, he replied: “I liked them.”
When asked about the reaction to his speech, he replied: “I like my comments.”
Trump also said it was “great” to be in Doonbeg and added: “I love the Irish.”
Taoiseach Micheál Martin and several other senior Irish government officials are also attending the final day of Irish Open play at Mr Trump’s Doonbeg course.
Mr Trump is expected to present the trophy to the winner at the Trump International golf resort in Doonbeg, Co Clare, before flying back to the US at the end of the two-day itinerary.
A major security operation continues as part of the visit, with An Garda Síochána liaising with the Defense Forces and US Secret Service in the resort area.
Trump’s presence sparked protests in Dublin and Clare, but Garda Commissioner Justin Kelly said there would be “no tolerance” for public disorder or attempts to influence the US president’s “critical movements”.
A small number of protesters gathered at Shannon Airport on Sunday.