It was only the Dragons' second win at BT Sport Cardiff Arms Park in the regional era, with the first coming in 2003-04, and gave the Dragons their fourth consecutive win in all competitions.
Tyler Morgan's first-half try gave Newport a 13-3 half-time lead over a Cardiff side who left Kiwi outside-half Gareth Anscombe and Wales prop Gethin Jenkins on the bench.
And after a penalty try for the visitors early in the second period, scores from Jarrad Hoeata and Tavis Knoyle were too little, too late for the Blues as they slipped to their first home loss in five games in all competitions.
"I think it's a fairly momentous day for us," said Jones. "It's a challenge coming to Cardiff. I came here with Ebbw Vale and Sale and it's a tough place to come.
"To win here for the first time in ten years will hopefully give us some confidence going forward.
"We were very good in parts. There are still things to improve, but we have to take a lot from it in terms of the psychology of getting an away win in a local derby, so it's a positive for us.
"We are very pleased, but it's half-time and the motivation is all with the Blues now.
"It's a big day but because it's one of these back-to-back ones, you've got to keep your feet on the floor and not celebrate too much because it will bite us next week if we do.
"It's about recovery and being fresh in mind and body for a big game on New Year's Day.
"It's important to celebrate the highs because there are plenty of lows in this game, but we will come back in to train ready to do the double."
As well as recording a fourth win on the bounce, Newport ended a five game hoodoo against Welsh sides in the GUINNESS PRO12, and Jones believes they may have turned a corner.
He said: "In the last four or five weeks we've had players back on their feet and have been able to prepare well.
"There is a lot more clarity in everybody's role and that is showing through. The biggest thing is the way the players have stuck through it.
"The spirit in the camp has been fantastic. Full credit to the players. It was a big game and they have come out on the right side."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletterfor regular updates on the GUINNESS PRO12
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland