The Tottenham Hotspur duo have been praised by the pundit.
The 19-year-old has started brightly at White Hart Lane, leading to his first England call-up - followed by another - but one Merson doesn't feel will be his last.
And the former midfielder says he is a big fan of the Tottenham talent.
Merson told Sky Sports on Thursday morning: "I'm a big fan of Dele Alli and I think he's going to get 50-60 England caps."
On Dier, meanwhile, Merson insisted he would also like to see the Tottenham midfielder playing for the Three Lions during their friendlies against Spain and France.
Peter Shilton leads the way in terms of England caps on 125, with David Beckham second, Steven Gerrard third and Bobby Moore fourth.
Former Tottenham stars around the 50-60 mark, meanwhile, include Chris Waddle and Paul Gascoigne.
The way Alli has started his Spurs career suggests there is absolutely no reason he can't amass as many England appearances as Merson suggests, while Dier will be in with a shout of a few, too.
The only thing that could worry Mauricio Pochettino, naturally, is the risk of injury if the Tottenham duo go all out against Spain, France or both.