Despite an early try for Gareth Wyatt the Irish had led after 20 minutes thanks to their only try of the night from Shane Horgan, which was converted by Felipe Contepomi, who also added a penalty.
However the Dragons hit back with two Ceri Sweeney penalties and Wyatt’s second try to set up a 16-10 lead at the interval – and it was a lead they never looked like relinquishing in the second period.
The home side looked to have the measure of Leinster in all areas of the second half and they eased further ahead with two further Sweeney penalties in quick succession before a breakaway try from Gareth Cooper compounded the misery for the Irish side.
Kevin Morgan rounded a fine individual display from full back when the collected the bonus point winning try for the Dragons late in the game.
After the game Dragons coach Chris Anderson was delighted with his side’s performance. "It was a great effort by the team. The forwards played great and held the middle, we’ve got some backs now that can really score tries. I enjoyed watching it.
"Gareth Wyatt had a great game, our backline did really well, the forwards set it up but the backline played really well," he added. "We need to keep building the momentum, with some big games coming up it helps us to work off a positive platform."