Kim Yo-jong is the first of North Korea's ruling family to visit the South.
The plane carrying a high-level North Korean government delegation including leader Kim Jong-un's sister arrived in South Korea Friday to attend the opening ceremony of the Pyeongchang Winter Olympics.
The entourage, which included the North's nominal head of state Kim Yong-nam and senior officials landed at Incheon International Airport in a private jet.
Kim Yo-jong is the first member of North Korea's ruling family to set foot in the South since the 1950-53 Korean War.
While Kim Yong-nam is the most senior North Korean official to make a cross-border trip.
During their three-day visit, the North Korean officials will meet with South Korean President Moon Jae-in, who is trying to use the Olympics as an opportunity to pull North Korea into meaningful talks over its nuclear programme.
The delegates briefly met a group of South Korean officials on Friday, including Unification Minister Cho Myoung-gyon, who greeted them at the airport, according to the ministry.
They were later scheduled to board a high-speed train to Pyeongchang.