The 20-year-old Cheltenham-born player, who can operate as a defender or holding midfielder, has joined the Barclays Premier League side from Portuguese club Sporting Lisbon, where he came through the youth ranks.
Having finalised his switch on a five-year deal for around £4million, the England Under-21 international told Spurs TV: "I am really excited to be joining such a big club.
"It has always been my ambition and my dream to come back to England and play in the Premier League.
"The reason I moved to Portugal was nothing to do with football - it was because of my family.
"We moved there when I was six, I got picked up by Sporting when I was eight and I went through their youth system, all the way to the first team
"It is kind of a strange background and everyone seems surprised by it
But it just happened that way really.
"At the beginning it was hard because I didn't really speak the language
I was seen as a bit of an outsider.
"But after I picked up the language when I was 12 or 13, it was really easy
I don't think they saw me as English - they pretty much saw me like one of their own.
"The Premier League was still the only league I watched really
It is on television in Portugal and it is the biggest league in the world in my opinion.
"Obviously I've watched a lot of Tottenham, and I've always enjoyed the way they play, their attacking football
"I think, coming from Portugal, that suits me and this season I just want to adapt really quickly to the Premier League and do the best I can."
Dier, who had a spell on loan with Everton in 2011 to further his experience, made 26 league appearances overall for Sporting after making his debut in November 2012.
Source : PA
Source: PA