Mr Trump’s helicopter took off from US Army Garrison Yongsan in Seoul – but then turned back, US officials said.
The US leader, who is on a two-day visit to South Korea, is due to address South Korea’s parliament shortly.
On Tuesday, he urged Pyongyang to “come to the table” and discuss giving up its nuclear programme.
The president has previously threatened “fire and fury” against Pyongyang, prompting a strong reaction from North Korea.
Mr Trump is on a five-nation tour of Asia, and discussing North Korea’s nuclear ambitions has been high on his agenda.
The visit to the heavily fortified DMZ was cancelled due to fog, White House spokeswoman Sarah Sanders said on Wednesday.
She added that the president was frustrated and disappointed.
He was due to join South Korean President Moon Jae-in at the DMZ. Mr Moon had already arrived in the area.
The White House had previously said Mr Trump had no plans to go the DMZ, describing the destination as “becoming a little bit of a cliche”.
Various US presidents and officials have visited the area on past tours.
Early on Wednesday, reporters accompanying President Trump were informed he would be going after all – yet he was soon thwarted by bad weather. (Courtesy BBC)