Wales wing Jones crossed three times in the space of 14 minutes in the first half to virtually seal the result inside half an hour. Dafydd James added two while Lee Byrne completed the rout to move the Scarlets to within touching distance of Heineken Cup qualification.
The win was a first for coach Gareth Jenkins since applying for the Wales job after three successive defeats including the Powergen Cup Final, but opposite number Paul Turner will nw be looking at the end of season play-off against Italian opposition to return to Europe's top level.
Given the Dragons' abysmal record away from Rodney Parade, they have won one of their last 21 away games, Turner fielded a weakened team with his eyes on a crucial bottom of the table clash with Glasgow next week, and he was made to pay with a blistering display of counter-attacking rugby by the Scarlets and Jones in the first half.
They stole possession in midfield, Matthew Watkins saw Jones with bags of space out wide and the Wales wing did the rest from 65 metres, beating Jamie Ringer and Leigh Hinton with ease on his way to the line. His second was far easier after Iestyn Thomas handed him the try following Watkins's clever cross-field kick and he completed his hat-trick, the first by a Scarlets player in the Celtic League, after the Dragons coughed up possession once again.
Inoke Afeaki and Matthew Rees combined to release Jones inside his own half. The left wing, who returned to the Wales team this season following a three-year absence through injury, revelled in the space and cantered down the pitch to score.
James then added a try in each half as the Scarlets ran riot while Byrne also went over when the Scarlets were down to 14 men after Rees's yellow card. Jones proved as lethal in defence as attack with try-saving tackles on Nathan Brew and Gareth Chapman. Brew, the Dragons' liveliest threat, was rewarded for his efforts with a late try that was followed by Jason Forster but it too late to prevent a handsome Scarlets win.
Scarlets: (24) 36
Tries: M Jones (3), D James (2), Byrne
Cons: C Thomas (2), Hercus
Dragons: (3) 17
Tries: Brew, Forster
Cons: A Thomas (2)
Scarlets: Lee Byrne; Dafydd James (capt), Matthew J Watkins, Regan King, Mark Jones; Ceiron Thomas, Clive Stuart-Smith; Iestyn Thomas, Matthew Rees, Craig Dunlea, Adam Jones, Chris Wyatt, Inoke Afeaki, Dafydd Jones, Alix Popham
Replacements: Phil John, Aled Gravelle, Jonathan Mills, Jonathan Edwards, Liam Davies, Mike Hercus, Garan Evans
Dragons: Leigh Hinton; Gareth Wyatt, Nathan Brew, Jon Bryant, Ben Breeze; Aled Thomas, James Ireland; David Maddocks, Andrew Brown, Gethin Robinson, Bryn Griffiths, Peter Sidoli, Rhys Oakley, Michael Owen (capt), Jamie Ringer
Replacements: Adam Black, Chris Anthony, Andrew Hall, Jason Forster, Gareth Chapman, Ceri Sweeney, Gareth Baber
Referee: Nigel Whitehouse (WRU)