The club posted the following message on their Twitter account:
"The England international midfielder was diagnosed with appendicitis after contacting our medical staff due to acute abdominal pain," read a statement on the club's official website. "He received immediate treatment to assess and then remove the appendix."
Per Dan Kilpatrick of ESPN, the England international's predicament leaves the team light in midfield for the busy festive period:
Dier missed Saturday's 1-0 win over Burnley, which saw Christian Eriksen net a stoppage time winner for Spurs. Teenage midfielder Oliver Skipp, 18, made his full Premier League debut for Tottenham in the victory.
It was initially reported by Alasdair Gold of Football.London that Dier was suffering with a virus.
The layoff comes at the worst possible time for Tottenham manager Mauricio Pochettino, as his team gear up for the busiest spell of the season.
Spurs take on Arsenal in the Carabao Cup quarter-final on Wednesday, before they travel to Everton on Sunday for a Premier League clash.
Dier's versatility, energy and consistency would have made him a key man for Tottenham in the coming weeks.
While there are more important players in this Spurs squad than the former Sporting CP man, Pochettino clearly sees the value in Dier, having started him in 13 of his side's 17 Premier League games this term.