Sarr had already set up Emmanuel Dennis for his first club goal for Watford’s opener before he found the net himself after an individual run down the right for his side’s second.
Debutant Cucho Hernandez added the home side’s third just moments after coming on but Aston Villa were able to reply through John McGinn’s long-range effort.
In added time, referee Mike Dean pointed to the penalty spot after a foul in the box, with debutant Danny Ings stepping up and making no mistake for his new club, firing the ball into the back of the net.
Sarr had joined Watford for their last Premier League campaign for a club-record fee in the summer of 2019 but struggled in a tumultuous season for the club, finishing with just six goals.
The following Championship season however, the 23-year-old finished with 13 goals to his name and impressed on his top-flight return, forcing Villa manager Dean Smith into an early half-time substitution after he had got the better of defender Matt Targett on a number of occasions.
It was a return to full stadiums for the fans, but the visiting contingent will not have been too pleased with their first look at a post-Jack Grealish Aston Villa, who looked lacklustre in midfield and had to wait until the 70th minute for their first shot on target.
Watford did not have to wait long for their first Premier League goal of the season, when debutant Dennis slotted the ball home in the 11th minute.
Captain Tom Cleverley had played in Sarr down the wing, but it was the Senegal international who did the work, driving down the right and getting ahead of Targett before picking out Dennis in the centre.
The 23-year-old’s first effort was blocked with cries of handball, but he made no mistake with the rebound, firing the ball under goalkeeper Emiliano Martinez.
However, just moments later, Sarr – who had been causing problems for the Villa defence all throughout the first half – wove his way down the right before shooting high and past Martinez to double the lead.
It was a frustrating opening 45 minutes for the visitors as they struggled to get forward and create space for their debutants at the top end of the pitch with Ings and Emiliano Buendia only seeing the ball sporadically.
Villa started the second half brightly, with one effort going across the face of goal and half-time substitute Jacob Ramsey firing a long-range effort over the crossbar, however their early energy did not turn into many clear-cut chances.
Smith’s side were still without a shot on target when Hernandez looked to have put the game past Villa just moments after coming on for his Premier League debut.
The 22-year-old Colombia international received the ball down the left and drove forward, opening up space before curling the ball expertly past Martinez to open his account for the season on his senior debut.
However, just three minutes later, Xisco Munoz’s hopes of ending his first game of the season with a clean sheet were over when another debutant, Leon Bailey, set up McGinn on the edge of the area, and the midfielder fired the ball into the top of the net.
Ings’ late penalty was not enough for the visitors, with just seconds remaining on the clock before the whistle blew at Vicarage Road as Watford secured a win on their return to the top flight.
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in