In a weekend of enticing rivalries, Patchell - who will leave the Blues this summer - played a prominent role in a clash that kept spectators guessing throughout.
The Dragons looked to be in control of the clash, holding a 17-6 lead midway through the first half following Ashton Hewitt's try.
Their visitors staged a fightback and when Tom James crossed over, Patchell had the opportunity to level the scores with the conversion.
He missed that kick but earned a late reprieve from the tee when the Dragons conceded a penalty and this time the Welsh international made no mistake.
That was not the only Welsh nail-biter of the weekend, however, after Ospreys edged home at Parc y Scarlets on Boxing Day.
John Barclay and Aled Davies crossed over for Scarlets, while Alun Wyn Jones, Hanno Dirksen and Eli Walker dotted down for the visitors.
Much like the clash at Rodney Parade it all came down to a late penalty but Steve Shingler fired wide and Wayne Pivac's charges were beaten.
Scarlets stayed top of the pile, however, as Connacht slipped to a low-scoring defeat at home to Ulster.
Nick Williams grabbed the only try of the game as the Ulstermen clinched a 10-3 triumph at the Sportsground to move into the top four.
Zebre moved six points clear of bottom club Benetton Treviso with a 28-25 victory in the first of two quickfire Italian derbies.
Treviso looked to have staged a superb comeback, only for Andries Van Schalkwyk to cross over late on and inflict their 21st straight defeat in all competitions - though they did clinch a seventh losing bonus point in ten league games.
Edinburgh grabbed the initiative in the 1872 Cup with a 23-11 victory over Glasgow Warriors at BT Murrayfield, man-of-the-match John Hardie crossing over on his inter-city debut.
And Leinster silenced a packed-out Thomond Park as Isa Nacewa, Jack McGrath and Zane Kirchner each crossed over to inflict a 24-7 defeat on Munster and push them back to sixth in the table.
TRY OF THE WEEKEND
The Dragons made a flying start at Rodney Parade on Sunday and after just ten minutes they had the try of the weekend, courtesy of Ashton Hewitt.
The winger collecting a long miss-pass by the left touchline and looked up to see a pair of Blues defenders standing in his way.
But the 21-year-old showed all the class of an international winger to brush off the pair of them, stay inside the touchline and reach out to score in the corner.
BREAK OF THE WEEKEND
Garry Ringrose is making a name for himself as a future star of Irish rugby and he wasted no time in making himself known against Munster on Sunday.
With just three minutes on the clock, the young centre received the ball on his own ten metre line and showed off his searing pace to leave a string of defenders for dead.
All that was left was for Ringrose to offload to the supporting Isa Nacewa and Leinster were on their way to a vital derby win.
PLAY OF THE WEEKEND
Just as the boot of Aled Thomas looked to be edging Scarlets towards victory on Saturday, Eli Walker struck with a vital try for Ospreys.
However, it was not a try of the Wales winger's making - rather the result of an impressive break from Moldovan prop Dmitri Arhip.
The front rower found some space down the left touchline and burst into it before displaying his composure to draw in the final defender and hand off to Walker.
PLAYER OF THE WEEKEND
John Hardie is fast-becoming a prominent figure in Scottish rugby and he did that cause no harm at BT Murrayfield on Sunday.
After impressing at the Rugby World Cup, Hardie stole the show in his first inter-city rivalry, crossing over at the back of a powerful rolling maul amid a gut-busting performance.
The flanker was named man of the match as Edinburgh put themselves in pole position to retain the 1872 Cup.
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