Having improved immeasurably in recent weeks, the visitors bagged a deserved success against a Scarlets side who were hoping to take a significant step closer to the WRU age grade championship final.
Jac Williams, Andre Hughes and Andrew Oakden helped themselves to tries for the North, with Alex Schwarz adding a penalty and two conversions for good measure.
Leading try scorer Gethin Hunter and Gareth Thomas replied with tries for the Scarlets whilst Jordan Williams kicked a conversion and penalty.
However, it was all too little too late for the Scarlets as Gogledd Cymru held on for a famous win.
There was no such joy for the Under 18s who went down 25-0 to the Scarlets, also at Llandovery.
Two penalties from the boot of Steven Shingler gave the Scarlets a modest six point advantage at the interval, but in the second half, there were tries from Lee Rees (2) and Lawrence Reynolds.
Shingler added two conversions, but the Scarlets were disappointed not to have secured a bonus point for four tries.
Victory leaves the Scarlets seven points clear at the top of the league with only one game remaining for them.
