Trump's met with President Moon Jae-in at the Blue House, where the South Korean leader has his offices and home.
Trump also met EXO, a star pop group whose members gave the president a book. The group also chatted with Trump's daughter, Ivanka, and his son-in-law, Jared Kushner.
The president isn't saying whether he'll meet North Korea's leader Kim Jong Un on Sunday at the heavily fortified South Korean-North Korean border known as the DMZ.
Trump is just saying "it will be very interesting" but he's not giving other details about the surprise trip, which he announced earlier in the day on Twitter.