Leinster’s power eventually told as two penalty tries helped them continue their fine form in the PRO12 and moved to the top of the table with this win over the Welsh in Dublin on Friday night.
Jack McGrath and Darren Hudson also got on the scoresheet for Leinster, who were given a sizable scare by two tries in three minutes shortly after the break for the Dragons, but came away with all five points on offer.
It was a fifth win in their last six PRO12 matches for Leinster but quickfire tries from Ashley Smith and Richie Rees had threatened an upset at the RDS.
Ian Madigan had put the hosts ahead, with Jason Tovey levelling at 3-3 with a drop goal.
The defending RaboDirect PRO12 champions finally had their first try of the match on 38 minutes when McGrath forced his way over and Madigan made it 10-3 at the break.
Quick fire tries from Smith and Rees and a penalty from Tovey had the Dragons 16-10 ahead early in the second half.
Two penalty tries saw Leinster lead 22-16 after 67 minutes, with Tovey getting a penatly to keep them within losing bonus point range.
Dragons’ night ended on a bad note when Nahuel Tetaz Chaparro was shown a red card in the final minute for a tip tackle on Isaac Boss and Leinster rubbed salt into the wounds with a Hudson try.