More than 3,000 Bluebirds fans and Cardiff City staff in and around the away dug-out gave Aron Gunnarsson a standing ovation at Old Trafford.
Gunnarsson made way for Jazz Richards in his final appearance for Cardiff before heading off to play in Qatar next season.
The Icelandic warrior has been a loyal servant to Cardiff, often playing through injuries to help the team.
After the final whistle Gunnarsson led his Bluebirds team-mates over to applaud travelling fans.
It was fitting that Gunnarsson should sign off with a win against Manchester United away.
This was a first win for the Bluebirds against Manchester United for almost 60 years.
Cardiff were bright, aggressive, enthusiastic and dangerous at a stadium where the atmosphere seemed odd.
Home fans in the near 75,000 attendance were downbeat and quiet, while the City faithful were having a ball, cheering, chanting, singing and thoroughly enjoying themselves. It was party time in the away section.
Sir Alex Ferguson looked on in horror from his grandstand seat.
Nathaniel Mendez-Laing scored both City goals, but this was a complete Cardiff team display.
“This is a massive win for the club,” said Mendez-Laing. “It’s disappointing to be relegated, but we are in the best league around the World.
“We’ll rest over the summer and come back refreshed. With performances like this we should be okay.
“Every player wants the gaffer (Warnock) to stay. Nobody knows the Championship better than he does and he has a great relationship with the players.”
Former Bluebirds manager Ole Gunnar Solskjaer must have felt terrible as his team were outfought- and thousands of home spectators were leaving well before the end.
Goalkeeper Neil Etheridge scarcely had a second half shot to save, while Cardiff created the better chances.
Neil Warnock made two changes to his Bluebirds team, calling in Leandro Bacuna and Kenneth Zohore for Victor Camarasa and Danny Ward.
City had good reason to feel satisfied with their first half performance, having had the edge over the opening 45 minutes.
Captain Sean Morrison and his team led 1-0, having played as an organised unit.
Leandro Bacuna and Aron Gunnarsson played in front of the back four, shielding the defenders behind them.
That allowed the front four of Josh Murphy, Mendez-Laing, Zohore and Bobby Decordova Reid opportunities to give United’s back five a hard time.
Zohore, in particular, was a threat. He used his pace and strength to keep home defenders ill at ease.
Manager Ole Gunnar Solskjaer was forced to tweak his teams playing system for the second time because City had the edge and the home team were booed off at half-time.
United sent on Anthony Martial in a bid to improve their attacking
options with Paul Pogba dropping into a deeper role.
Martial was causing problems for and Warnock responded by sending on Jazz Richards for Gunnarsson after 58 minutes.
Lee Peltier was assigned to stick closer to Martial and diminish that threat.
Cardiff went ahead after 23 minutes when Mendez-Laing was brought down Diogo Dalot. Referee Jonathan Moss pointed to the penalty spot and Mendez-Laing jumped up to score from the spot.
That penalty came after Pogba conceded possession on the edge of United’s penalty area.
Mendez-Laing fired City 2-0 ahead with 54 minutes gone after some outstanding work by Josh Murphy.
The winger showed great composure when he ran into United’s penalty area, drew defenders to him and squared a pass for Mendez-Laing to fire home.
Remarkably, Mendez-Laing was completed unmarked in front of goal as he scored.
It was a feelgood win at the end of a season in which Cardiff have been relegated.
But there is a genuine feeling that City can bounce back and City fans made their thoughts clear, chanting: “Neil Warnock, we want you to stay.”