Will Thomas marked his return to action after a three-month injury lay-off by opening the scoring for the Blue and Blacks, Ceiron Thomas adding the conversion. A Geraint O'Driscoll penalty took the sides into the break with the match delicately poised at 3-7.
Hooker Ethan Lewis extended the visitor's advantage with a try early in the second half which was also converted by Ceiron Thomas. Once again Geraint O'Driscoll pulled Newport back into the game with a penalty to make it 6-14.
Cardiff piled on the pressure and forced a fumble on Newport's own try line. A well-worked scrum followed and number 8 Luke Hamilton sealed the victory touching down between the posts. Rory Budina scored a consolation try for the home side 9 minutes into injury time but it was not enough to deny Cardiff a famous victory.