Jang and Lee defeated the Finnish team of Oona Kauste and Tomi Rantamaeki 9-4 at Gangneung Curling Centre in Gangneung, reports Yonhap news agency.
Mixed doubles curling is being contested for the first time at these Olympic Games.
The South Koreans lost their second match on Thursday to China in overtime by the score of 8-7.
Against Finland, the South Koreans set the tone early by scoring three points in the first end, and added a point each in the second and third end for a 5-0 lead.
Finland cut the deficit to 5-4 after six ends, but South Korea earned four more points in the seventh end to clinch the victory.
"At first I was really nervous and felt burdened," Lee said after the first match.
"But I was also encouraged by the spectators' cheering."
More than 2,000 fans came to the Gangneung Curling Centre for the event.
Jang said she wished to thank the spectators for their understanding manners while watching curling events.
"They were silent when we made shots, and applauded after. They knew the rules well, and I was thankful," Jang said.
"I am glad to bring the first victory to South Korea. I hope this will inspire other athletes to make efforts too," Jang added.
Facing the Chinese duo of Wang Rui and Ba Dexin, Jang and Lee found themselves down 6-1 after four ends but rallied with four points on a "power play" in the fifth.
Teams can only have one power play per game, when they have the hammer. Instead of putting their rock in the centre, the team can choose to place two stones to the side of the sheet and set up a scoring opportunity.
China, the bronze medallist at last year's world mixed doubles championships, got a point back in the sixth, but South Korea answered with two points to tie the score at 6-6. China picked up the clinching point in the ninth end.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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