Carrick, who will join United manager Jose Mourinho's backroom team from next season, was handed the captain's armband for his final game at Old Trafford and given a guard of honour as the teams emerged for kick-off.
And it was the former England midfielder who made the decisive contribution, his superb lifted throughball enabling Juan Mata to tee up Marcus Rashford to break the deadlock.
That was the lone piece of invention from a United side minus the services of Anthony Martial, who was left out of the squad amid rumours of a move away, though MUTV later suggested the France international has an injury.
However, the victory was rarely in doubt after they went ahead, Watford struggling to craft much in reply as United finished on 81 points, the 19-point gap to champions Manchester City an illustration of the improvements the Premier League runners-up must make next season.
Early on United played with a lack of intensity perhaps befitting of a side focused on a cup final.
As a result Watford found plenty of openings in the United defence on the counter, though they struggled to exploit them, but the visitors were dealt a blow when Christian Kabasele was forced off through injury after falling awkwardly into the advertising hoardings.
And Watford's inability to take advantage of United's lackadaisical start was punished as Carrick provided a wonderful flourish of creativity to mark his Old Trafford farewell.
He lifted an expertly weighted ball over the Watford backline, with Mata beating the offside trap and controlling it brilliantly before squaring for Rashford to tap into an empty net.
17 - Marcus Rashford has been directly involved in 17 goals in his last 18 starts in all competitions at Old Trafford (9 goals, 8 assists). Effective.— OptaJoe (@OptaJoe) May 13, 2018
United were grateful to Sergio Romero for preserving their lead a minute before half-time, David de Gea's understudy springing to his left to turn Richarlison's point-blank header from Daryl Janmaat's cross behind, with Gerard Deulofeu firing into the Argentine's midriff from the subsequent corner.
Such moments of excitement were thin on the ground in an extremely pedestrian second half in which Watford, who ended the campaign in 14th as a result of this defeat, finished the stronger.
But there was still a moment to remember late on as Carrick's 464th United appearance came to a close, receiving a standing ovation as he was replaced by Paul Pogba on a day that belonged to one of the club's most distinguished servants.
Key Opta stats:
- The Red Devils won all 21 of their Premier League matches this season when they scored first, only the second team to achieve this in a Premier League season (also Portsmouth in 2007-08).
- Under Javier Gracia, the Hornets have attempted 61 shots in away Premier League games without scoring.
- Michael Carrick made his 481st and final Premier League appearance – this was his first start in the competition for 364 days (May 14th 2017 against Spurs).
- Sergio Romero has kept six clean sheets in seven Premier League matches for Manchester United.
- Since the start of last season, Manchester United have kept more Premier League clean sheets than any other team (36).