And the win was even remarkable given that the Steelmen trailed 11-3 at half time, their comeback helped by a vital score from Polu Uhi.
It was a poor start for the visitors though as they went behind to a Joe Griffin penalty after just five minutes. And the Premiership side were further ahead 15 minutes later when an Ebbw lineout went horribly wrong and opposition lock James Murphy trotted over unopposed.
With the game taking place in the middle third, scoring opportunities were few and far between but after half an hour, outside half Josh Lewis opened the Steelmen'saccount with a penalty.
Two minutes before half time, a Griffin penalty struck an upright and rebounded into Blue and Black hands. Ebbw defended fiercely and, according to referee Mr Ian Davies, unfairly. Ebbw's Adam Jones received a yellow card and Griffin made it 11-3 to Cardiff at half time.
Down to 14, Ebbw came out a different side in the second half and took the game to their Premiership opponents.
Despite keeping the Steelmen out, the pressure eventually told for Cardiff and Lewis added a beautifully struck second penalty to bring the scores to 11-6.
Within minutes, Ebbw were level, a sweeping move down the left seeing the powerful Uhi take the ball 30 metres out and round the Cardiff full back to cross under the posts. Lewis converted and the Championship side led.
With Spencer Gibson punching holes in the home defence every time he got the ball and Ebbw's scrum on top, Cardiff scrambled to keep Ebbw out, often illegally.
Another opportunity inevitably came Lewis's way and he made no mistake, taking the lead to 16-11.
Cardiff looked down and out, with outstanding No. 8 Luke Hamilton their only beacon of hope.
And although the referee found 15 minutes of extra time and issued yellows to Cameron Reagan and Ronny Kynes, the Steelmen held on for a famous win.