Kim's visit marked the first time any member of North Korea's ruling family had visited the South since the Korean War which ended in 1953 and warmly shook the hand of Moon during a politically-charged spectacle.
There was no such greeting between Kim and United States Vice-President Mike Pence, whose comments regarding sanctions on the North earlier this week prompted the country to threaten to withdraw from Pyeongchang 2018.
insidethegames exclusively revealed yesterday that North Korea had been persuaded to stay at the Games following meetings with the International Olympic Committee (IOC) and other stakeholders.
South Korea news agency Yonhap reported Pence also made only a brief appearance at a pre-Opening Ceremony reception dinner hosted by Moon.
Pence and Kim were sat close together during the Ceremony, providing an image that belies the current tension between the two countries.
It was claimed, however, that the US Vice-President did not stand when North and South Korea entered the Stadium during the parade.
Moon later officially declared the first Winter Olympic Games to be held in South Korea open.
It came after athletes from North and South Korea, who are still technically at war, marched under the unification flag to bring the athletes' parade to a close.
North Korea ice hockey player Chung Gum Hwang and South Korean bobsledder Won Yun-jong were joint flagbearers.
It was the first time since Turin 2006 that the two nations had marched together.
They were met with a warm reception from the crowd, in contrast to the cold response given to the Olympic Athletes from Russia (OAR) team, competing as neutrals after the IOC ruled they had committed a "systematic manipulation" of the anti-doping system at Sochi 2014.
It also came despite anti-North Korean demonstrations before the Ceremony and amid uncertainty as to how athletes from the country would be received.
IOC President Thomas Bach delivered his speech in front of the Korean athletes in another symbolic gesture, before two members of the joint women's ice hockey team passed the Olympic Torch to figure skating legend Kim Yuna to light the Cauldron.
"You can only really enjoy your Olympic performance if you respect the rules, and stay clean," said Bach.
"While you compete with each other, you live peacefully together in the Olympic Village, respecting the same rules, sharing your meals and your emotions with your fellow athletes.
"This is how you show that in sport we are all equal.
"This is how you show the unique power of sport to unite people.
"A great example of this unifying power is the joint march here tonight of the two teams from the National Olympic Committees of the Republic of Korea and the Democratic People's Republic of Korea.
"We thank you."
Pyeongchang 2018 President Lee Hee-beom also paid tribute to the joint marching of the two nations.
"The entire world watched and witnessed another historic joint marching of the South and North Korean athletes under the Korean Peninsula flag," he said.
"It means two Koreas became one unified Korea through the Olympic Games.
"Sport has a great power to unite people and bring together the world in harmony and peace transcending disputes and conflicts.
"The Pyeongchang Games, I am confident, will provide a light of hope for all global citizens yearning for peace on this planet."
The OAR team entered the Ceremony having suffered a blow this morning, when the Court of Arbitration for Sport dismissed the appeals of 45 athletes who were hoping to be cleared to compete here.
Tonga's flagbearer Pita Taufatofua marching topless for the second consecutive Olympic Games Opening Ceremony provided a light-hearted moment among all the diplomacy and politics.
The oiled-up Taufatofua, due to compete in cross-country skiing, entered the arena in a similar manner to the Summer Games in Rio de Janeiro in 2016 despite the freezing temperature.
The Ceremony was packed full of Korean culture and included a performance of John Lennon's Imagine, sung by rock star Jeon In-kwon and singer-song writer Lee Eun-mi, various K-pop hits and a crescendo of fireworks to end the evening.