Ferguson joined Brighton from Bohemians in January 2021 but his breakthrough season has been the current campaign.
The 18-year-old Republic of Ireland striker has made 19 appearances this season and scored eight goals.
His goal tally includes four in 13 Premier League appearances.
Ferguson is the latest Brighton player to pen fresh terms at the club in recent months, joining the likes of Moises Caicedo, Solly March, Adam Lallana and Pascal Gross.
Ferguson missed Brighton's FA Cup semi-final defeat to Manchester United last week because of a foot injury and is a doubt to face Nottingham Forest in the Premier League on Wednesday.
Brighton manager Roberto De Zerbi said on the club's website: "Evan's contract extension is great news.
"He trains and plays like a senior player with many years of experience and has become an important member of the squad. The aim is to help him become one of the strongest strikers in Europe."
"It's very important news. He can improve a lot with us.
"In Brighton, there are the right conditions for the young players and he's still 18. We have to not forget that.
"He's playing very well. With the Man United (game), it was bad for us without him because he has different qualities, he can give us different solutions in the last 20, 30 metres.
"I don't want to take any risks with him. We have another nine games and maybe he can be important for the last eight, if there is some risk (against Forest)."
