England centre Jamie Noon grabbed a try in each half and John Rudd added a third late in the game as the Falcons kept alive their hopes of qualifying for the knock-out stages by completing a 25-9 win at Kingston Park.
Newcastle cashed in on a lively opening spell with a ninth minute drop goal from Tom May but Ceiron Thomas slotted a penalty shortly afterwards when Noon strayed offside.
"It was our best performance of the season," said Newcastle director of rugby Fletcher.
"Our platform was solid and our midfield of Toby Flood, Jamie Noon and Joe Shaw were solid and Jamie got a couple of tries, but all the players did well, especially the forwards who were outstandingly led by Phil Dowson.
"We had 21 Englishmen out there tonight so we're doing our bit for English rugby, but we won't be going overboard with this result just as we don't over-react to a defeat."
Fletcher also paid tribute to Flood but urged England not rush him.
"Toby is right where he should be and he's not yet ready for the full England international scene," said Fletcher.
"He's in the England Academy side and that's about were he is. That's just my opinion and it's not my call but I wouldn't like to see him rushed.
"We worked really hard in training and we got our reward tonight."
Double try scorer Noon was not hanging about after his side's 25-9 win either.
The England and Newcastle Falcons centre was off home as quick as he could with his wife Rachel expecting their second child.
"I've been a bit away with the fairies this week," admitted Noon, who scored a try in each half and could have had a hat-trick. "But I just happened to be in right place at the right time for both tries.
"To be honest I really didn't know too much about either of them - the first one came when I just went through a gap and the second the ball was bouncing around like a ping-pong ball and it came to me and I went for the line as best I could.
"It's a massive win for us and it will do the team's confidence a power of good."