The central-defender has signed a one-year deal with the Reds, becoming Danny Wilson’s eighth signing of the summer, after joining from the Hornets for an undisclosed fee.
“Having interest from here wasn’t something I was going to turn down,” said Brown.
“I need to start playing games. My natural position is a centre-back but wherever the Manager decides to play me, I’ll definitely try my best.
Born in Manchester, the 22-year-old graduated from Manchester United’s Academy and spent time out on loan with clubs such as Oldham and Coventry before joining Watford in July 2013 on a permanent deal.
“It’s a young group and the lads have been great with me. The facilities are great and I’ve been before with the youth team.
“The Manager’s told me to keep working hard and the rewards will pay off. I’ll work hard in training and aim for as much game-time as I can.”