The US head of state, who the White House had previously said would not go to the symbolic spot, left his hotel in Seoul early in the morning and went to the Yongsan military base in the city, but his helicopter to the DMZ had to turn back due to weather conditions.
Visiting US presidents have regularly gone to the DMZ, where soldiers from North and South Korea face off along a border marked by concrete blocks between emblematic blue huts.
Administration officials had said before Trump's Asia tour that he would not be going to the spot, deriding the destination as "becoming a little bit of a cliche, frankly" after visits by Vice-President Mike Pence and Defense Secretary Jim Mattis.
But reporters accompanying the president were summoned earlier than scheduled Wednesday and press secretary Sarah Huckabee Sanders told them: "This is where we're going," holding up a piece of notepaper on which the letters "DMZ" were scrawled.
Trump's helicopter Marine One took off from Yongsan, but was forced to turn back. They waited nearly an hour for conditions to improve, but the weather worsened instead and the trip was abandoned.
Sanders said South Korean President Moon Jae-In had been scheduled to join Trump at the DMZ, in what she believed would have been a "historic moment" as the first time US and South Korean presidents had visited it together.
"The effort shows the strong and importance of the alliance between the two countries," Sanders said.