Luke Price set them on their way with a try after 25 minutes which Harry Allen converted and although they had to withstand heavy pressure, they managed to hold on in a frantic finale.
The Scarlets drew level 12 minutes after the restart when Ashley Stephens crossed for a try that David Newton converted, but back came the North with a try from the outstanding flanker Sam Studley. Allen once again improved the try to put the North back in front and although David Zagouras added a second try for the Scarlets, they were unable to snatch the winning score.
Blues South made it a double for the region with a 17-14 victory over the Dragons at Rumney.
Robert Grey and Stuart Maguire helped themselves to tries for the Dragons - one either side of half time - with Ben Farley and Danny Ellis adding conversions.
However, Ryan Moore and man of the match Joe Xiberras helped the home side into a 12-7 interval lead and Kyle Hally's second half try and a conversion from Joe Deacon made sure the points stayed at home..
Gafyn Cooper, high performance manager for the region said, "That's a great double for the region, I'm delighted for both sides because we have worked so hard."