The 24-year-old was absent from Spurs’ 1-0 win over Burnley on Saturday to remain just five points off the top of the Premier League in third.
“The England international midfielder was diagnosed with appendicitis after contacting our medical staff due to acute abdominal pain,” Spurs said in a statement.
“He received immediate treatment to assess and then remove the appendix.
“He will now undergo a period of recovery before commencing rehabilitation and it is expected he will return to training with the squad in January.”
Dier will miss Wednesday’s League Cup quarter-final against north London rivals Arsenal, as well as Premier League meetings with Everton, Bournemouth, Wolves and Cardiff in the next fortnight.