The decision was struck between North and South Korean sporting officials while the athletes were on their way to the Mongolian capital on Wednesday.
"We heard we will be a united team after we arrived in Ulaanbaatar," South Korea's team coach, former world champion Jeon Ki-young, told AFP on Friday.
"We are excited that the North Korean team is collaborating with South Korea. We want to get the gold medal. Then we can (solve) big issues in the world," he said.
They will compete in their first team event together tomorrow, with the Unified Korean Flag adorning their judogis, or uniforms.
The team will use the traditional Korean folk song, Arirang, as their anthem.
Won Kyong Il, head coach of North Korea's judo team, declined to comment, saying that the side has "a tradition not to speak to the media especially before the match".
There are a total of 21 athletes on the separate teams -- seven men and seven women from South Korea, and two men and five women from the North.
Therefore, according to championship rules, the two Koreas will need to choose five male and five female judokas from the Korean peninsula to play for the United Korea team on Saturday.
Teams from Mongolia, Japan, China, Taiwan, Macau and Hong Kong will also participate in the 11th annual tournament.
