Leinster missed the chance to go top of Pro12 as Jason Tovey helped Dragons upset the form book in a 23-13 victory at a wet Rodney Parade on Friday.
Dragons had won just one of their past six Pro12 fixtures to leave them second bottom of the table coming into this clash, but the impressive Ashton Hewitt and Tovey - who contributed 18 points - were on the scoresheet in a terrific first-half showing from the hosts.
Luke McGrath, captaining Leinster for the first time, scored in between those tries and the visitors pushed hard to turn the match on its head after the break.
However, Leo Cullen's men - devoid of the likes of Martin Moore, Isa Nacewa, Mike Ross, Cian Healy and Collie O'Shea - were unable to convert pressure into points in difficult conditions in Wales.
Dragons came flying out of the blocks and Hewitt found space on the outside to touch down in the third minute, only for a Fergus McFadden penalty and a fine solo effort from McGrath to put the visitors ahead.
The home side were then twice denied tries by the television match official, but Dan Leavy went into the sin bin as Leinster felt the pressure.
The numerical advantage paid dividends when Tovey touched down after a superb offload from Rynard Landman, before Tovey nailed a drop-goal to stretch the lead before the break.
McFadden split the posts early in the second half as Leinster applied the pressure, but Dragons soaked up the visitors' attacks and their seven-point lead was restored by Tovey's trusty boot.
Leinster's task was made even more difficult with seven minutes remaining when McFadden went into the bin for a dangerous charge on Sarel Pretorius at the breakdown and Tovey added another late penalty to clinch the win.