The Black and Ambers condemned The Chiefs to their first defeat of the season with winger Gareth Wyatt grabbing two tries in the opening period to put Newport on their way.
The home side led 18-0 at the break thanks to Wyatt and the boot of Chris Wannell. But a rearguard effort by the Chiefs saw No 8 Michael Stupple barge over before winger Nic Sesteret raced over late on but Newport repelled everything the Chiefs could throw at them to hold on.
Aberavon had to come from behind to fend off the challenge of Llanelli with a hard earned 16-19 victory.
Llanelli opened the scoring with a penalty by outside-half Dan Newton after just three minutes before stretching their lead on 17 minutes through a Dale Ford converted try.
Matthew Jarvis reduced the gap with two penalties before Newton took Llanelli out to a 13-6 half-time lead with another penalty.
But in the second half Aberavon hit back with 13 unanswered with a third Jarvis penalty which was followed by a converted try for David Pritchard. Jarvis and Newton swapped penalties again, but the Wizards held out.
Cardiff won 22-16 at the Arms Park over derby rivals Pontypridd in an intense affair. Ponty had a slender 3-0 lead at the break but a converted try by Kristian Baller and the boot of Gareth Davies edged the home side in front.
Earlier Ryan Howells raced over after intercepting 60m out and he completed the victory for the Blue & Blacks when outflanking the Ponty defence late on.
Neath stumbled to an 11-18 defeat against Bristol at the Gnoll where the visitors outscored the home side two tries to one.
For the English side, Ian Grieve and Sam Alford touched down with Neath's only response coming from Kevin Farrell.