With the Ospreys under 16s on top of the pile going into last night's game at Cross Keys, a fourth away-day success of the new season looked the most likely result.
However, having already beaten the Blues South and RGC 1404, the host region proved too strong for their visitors with team manager Colin Brennan delighted with the result.
"They are a good side, there is no doubt about that. However, we stuck in there and took our chances in the second half. We are obviously delighted to beat a side that was previously unbeaten," said Brennan, whose side are still on course to book a place in the play-offs.
Scrum-half Luke Crane set the Dragons on their way with a first-half try and though lock Deryn Jones was red carded shortly before half time, they made sure of victory courtesy of a second try from centre Hallam Amos and three penalties from the educated boot of outside-half Lloyd Rogers.
Full back Adam Rowlands scored the Ospreys' only try of the night, with outside-half Josh White adding a penalty.
However, it was not enough to snatch a result or even a losing bonus point as the Dragons held on to record a third win of the season.
Ospreys team manager Graham Court had no complaints about the final outcome.
"We came here in August for a pre-season friendly and saw how good they were. To be fair to the boys, we tried desperately hard in the second half to cut the gap, but we were unsuccessful and will take defeat squarely on the chin. There are no excuses - on the night, they were the better side."
Back at Llandarcy, the Ospreys under 18s bagged a bonus point in beating the Dragons 34-6.
Steffan Lewis crossed twice for the Ospreys with Rhys Thomas and Adam Wellington adding one apiece.
Ben Roberts and Sam Davies each kicked two conversions with Roberts adding two penalties for good measure.
Ethan Davies was the lone scorer for the Dragons - the outside-half kicking two penalties.
Elsewhere, Blues North under 16s defeated Blues South 19-8 at Abercwmboi, with outside-half Sam Withers helping himself to 15 points from a try, two conversions and a brace of penalties.
Oliver Smyth and Jon Barnett also crossed the whitewash, while for the South, outside-half Tom Smith scored a try and added two penalties and a conversion.
"It was good win, a hard-fought game and we're delighted to finish the first round of matches with four wins from five matches. However, it's certainly not a time to rest on our laurels as we have four away games to come," said team manager Nigel Way.