A converted penalty try and a try from Jack Liddiate kept the Dragons in the hunt in the first half, whilst tries from Alex Walker and Gavin Ferguson helped them into the lead with 20 minutes remaining.
Sam Mills added three conversions and dropped a goal, but Rhys Bloomberg, with a try, and a conversion and penalty from Dai Flanagan won the day for the hosts.
Player Development Manager Gafyn Cooper added ' this game was a great advert for regional rugby with the lead changing hands several times during the second half. There were some good individual performances for the Blues with wings Nick Gill and Gary Williams proving what clinical finishers they are.'
In the other game, in injury time drop goal from James Hook gave the Neath Swansea Ospreys a deserved 27-24 victory over the Scarlets.