Having reached the end of his contract at Emirates Stadium and seen no fresh terms tabled, the England international forward dropped into the free agent pool this summer.
Vicarage Road has been chosen as his new home, with the 28-year-old opting to remain in the Premier League rather than take on a new challenge elsewhere.
Explaining that decision, a product of Manchester United’s academy system told Watford’s official website: “There’s been long-standing interest from Watford and as I was a free agent this summer I had lots of talks with clubs from England and abroad.
“But I think this is the perfect place for me to come to, and that’s what I took into consideration whilst talking to various teams.
“I’m really looking forward to showcasing my talents, being back out on the pitch and playing football, doing the thing I love most.
“I think this is the right place for me to be and I’m looking forward to it.”
Welbeck saw injury struggles prevent him from making the desired impact at Arsenal, with just 14 appearances taken in during his final season in north London.
He is, however, adamant that he has plenty to offer Watford, adding: “There’s lots more to come. I know that I’ve got so much more to show the Premier League.
“It’s been frustrating at times but I can’t just dwell on that and let that get me down. I’m focused on now and being better than I ever have been.
“I’m feeling really good and really strong, and I’m looking forward to this challenge ahead.”
Welbeck is also looking forward to linking up with a couple of familiar faces, with Tom Cleverley and Craig Cathcart having risen through the youth ranks alongside him at Old Trafford.
A man with 42 England caps to his name said: “I know some of the boys already and they can’t speak highly enough of the club.
“I used to live in digs with Craig at United and I’ve spoken to Clevz a lot about the club. He said I’d really enjoy it here and thinks it’ll be a great match for me to come here.
“It seems like a great club with the whole surrounding environment. It’s a family-orientated place and that’s something that I value very highly.
“I’ve played against Watford and I like to watch football so I’ve seen them play on TV a lot and I know the team, and I think this is a place where I can really flourish.
“The squad we’ve got here is full of good players and people who I’m really looking forward to playing with and trying to push to that next level.”