The news was confirmed on Thursday, a day after Mason made his return to the Spurs line-up following a hamstring injury sustained in the 5-3 Premier League win over Chelsea on New Year's Day.
Mason started in Wednesday's League Cup semi-final first leg against Sheffield United and played 65 minutes before being replaced by Mousa Dembele.
After various loan spells at the likes of Doncaster Rovers, Lorient and Swindon Town, the midfielder has established himself in the first team at Spurs this season under the guidance of Mauricio Pochettino.
Mason has made 15 Premier League appearances so far in 2014-15, as Spurs aim to achieve a top-four finish and qualify for the UEFA Champions League.
The 23-year-old's fresh deal will keep him at the club until 2020.
