insidethegames revealed yesterday that the city would stage the event after the decision was made by the ANOC Executive Council at their meeting earlier this week.
ANOC secretary general Gunilla Lindberg made the announcement during the final day of the General Assembly.
Lindberg, a member of the International Olympic Committee (IOC) Executive Board, claimed North Korea would jointly host the gathering of the 206 National Olympic Committees in two years' time.
Representatives from South Korea and North Korea sent a letter to the Executive Council with the proposal, which the ruling body accepted.
It is expected, however, that the event would mainly take place in Seoul and it is not clear whether any part of the meeting would be held across the border.
The proposal comes after South and North Korea fielded a combined women's ice hockey team at the 2018 Winter Olympic Games in Pyeongchang, where they also marched together during the Opening Ceremony.
The two countries are set to launch a joint bid for the 2032 Summer Olympic Games.
Officials from the nations agreed to send a letter to the IOC confirming their intention to bid earlier this month.
The 2020 ANOC General Assembly will be the fourth of the last seven editions of the meeting to be held in Asia, following on from Bangkok in 2014, Doha in 2016 and this year's event here.