Kim Yo Jung greeted Moon Jae In, South Korea's leader, as the divided countries marched under a single flag at the Pyeongchang games.
Kim Jong Un's sister shook the hand of the South Korean president in a show of diplomacy, as the 2018 Winter Olympics got underway in Pyeongchang.
She smiled and shared a warm greeting with Moon Jae In, South Korea's leader, as the divided countries marched under a single flag in the contest's opening ceremony.
Kim Yo Jong was sent south of the Korean demilitarized zone by her brother Kim Jong Un, along with a delegation from their country.
US Vice-President Mike Pence was sitting nearby when the gesture took place.
He earlier decided not to shake hands with Kim Yong Nam, the man formally in charge of North Korea's delegation.
The games have turned into an opportunity to cool tensions between the two Koreas, after initial doubt that North Korea would participate at all.
Kim Yo Jong's visit marks the first time that a member of the Kim family has visited South Korea since the conclusion of the Korean War in 1953 and the beginning of the Kim dynasty's reign.
She is a mysterious figure who spent seven years completely out of the public eye.