The 20-year-old has emerged as one of the most talented midfielders in the Premier League since joining Spurs from MK Dons in 2015.
Alli's sparkling performances for Spurs this season have seen him linked with such clubs as Real Madrid, Barcelona, Manchester City and PSG but Dier feels his current club is much more likely to nurture his development for the good of his playing future.
"Yeah I think so, he's never mentioned to me once that it isn't," Dier told Sky Sports News HQ when asked if Alli would stay at White Hart Lane.
"I think he's fully motivated to do well with Spurs.
"He's still a very young boy, I think people need to remember that.
"I think he's at the perfect place for that because he's got a support system around him and a manager and a group of players that will take care of him.
"You have to worry about young players sometimes in certain places if they can cope with it and will they be looked after as a 20-year-old boy and not just an asset.
"I think he's very well looked after here and hopefully he will be for a long time."