Dendocker, 19, joins from Club Brugge after his contract with the Belgian club expired and he has agreed terms on a two-year deal at the Amex Stadium.
He will initially link up with Brighton’s under-23 squad and revealed he had spoken at length to his brother Leander – who plays for Wolves – about making the move.
“I’m very happy to be a Brighton player, it’s a lovely set-up which made it an easy choice to sign for the club,” he told the club’s official website.
“Graham Potter uses young players and that attracted me. Also, the stadium and training ground are fantastic and English football is the best in the world.
“It’s always been a dream of mine to play in England. I spoke with him (Leander) and he told me England is something you have to experience.
“He said there are a lot of good coaches that will help you and make you a better player – not just tactically but physically and every other aspect of the game. He said it was a lot of fun and that I had to do it.”
Brighton has been one of the busiest Premier League clubs since the transfer window opened and have already brought in England international Adam Lallana, defender Joel Veltman from Ajax and promising midfielder Jensen Weir from Wigan.