In an early Thursday morning tweet, Trump called it a "nice letter".
White House spokesperson Sarah Huckabee Sanders said President Trump received the letter on Wednesday.
"The ongoing correspondence between the two leaders is aimed at following up on their meeting in Singapore and advancing the commitments made in the US-DPRK joint statement,” Sanders said in a statement, using an acronym referring to the formal name of North Korea, Presstv reported.
However, Trump and the White House did not reveal more details about the letter.
Trump and Kim met on June 12 in Singapore, the first between a sitting US president and a North Korean leader, and signed a joined document, committing to establishing new relations and achieving peace on the Korean Peninsula.
Before the summit, the Trump administration said denuclearization should start "without delay," and after the meeting, it spoke of the process starting "very quickly."
So far, however, no concrete progress has been reported and Pyongyang has complained the Americans are making unilateral demands.
Kim, prior to the meeting, said that the two leaders had “decided to leave the past behind” and that “the world will see a major change.”
Trump said he had formed a “very special bond” with Kim and that Washington’s relationship with Pyongyang would be very different.
However, Trump on June 22 declared North Korea an "unusual and extraordinary threat" to the US as he acted to maintain harsh economic sanctions against Pyongyang.
"The existence and risk of proliferation of weapons-usable fissile material on the Korean Peninsula and the actions and policies of the Government of North Korea continue to pose an unusual and extraordinary threat to the national security, foreign policy, and economy of the United States," Trump said.