However, the Dragons made the worst possible start when Munster scored the game's opening try after 61 seconds.
A strong run from Paul O'Connell saw the ball find its way to centre Trevor Halstead, who crossed unchallenged straight from the kick-off. Fly-half Jeremy Manning, deputising for the injured Ronan O'Gara, added the extras.
The Rodney Parade crowd had been stunned into silence, but it wasn't long before they found their voice as the hosts hit back almost immediately.
The Dragons went through a series of phases before the fit-again Gareth Wyatt glided through the defence before slipping an inside scoring pass to Jason Forster with five minutes on the clock. Craig Warlow missed the conversion.
The Dragons, though, showed a lack of concentration from the restart, and a fumble by Ian Gough led to a Munster penalty by Manning.
It was thrilling stuff, but the entertainment was marred by a head injury to Munster's Manning after 28 minutes. He was carried off the field and was replaced by Paul Burke.
The reshuffle affected the Munster defence and the Dragons took advantage when wing Nathan Brew collected Ceri Sweeney's pass to glide over under the posts, with Warlow adding the extras to make it 12-10 in favour of the hosts.
And the home supporters were on their feet again deep into injury-time after a stunning try from Wyatt.
Brew began the move when he broke through before Sweeney and Aled Thomas combined to send Wyatt over to make it 17-10 at the break.
You sensed the Munstermen would step up the gears, and they did just and it saw Italian prop Frederico Pucciaiello touch down after finding himself in acres of space. Burke knocked over the conversion to level the scores at 17-17.
Warlow added two quick-fire penalties midway through the second half to give the Dragons some breathing space.
But the first offence came at a cost for the Dragons when Harlequins-bound Hal Luscombe sustained an arm injury following a late tackle and was replaced by Jonny Bryant.
But, as the rain began to fall, the Dragons just continued to defy the elements and the odds with a rousing performance.