The former Liverpool player was analysing Tottenham's 1-1 draw with Monaco in Europe on Thursday night when he made the positive comments about Alli, who played 90 minutes in the fixture.
The 18-year-old attacking midfielder had a big hand to play in Spurs' goal against the French outfit, and Hamann has been impressed with the way that Alli has settled into life in England's top-flight.
"He's been excellent," he said. "For a young player to come into the Premier League and make the impact he has made, after coming from Milton Keynes Dons for a pretty huge transfer fee for a League One player, he's been excellent. For a big lad, he has beautiful balance, he can travel with the ball and he can pick a pass."
Alli joined Spurs as one for the future, but he had a highly impressive pre-season and Mauricio Pochettino has rewarded him with regular starts.
Alli has now become a key part of Tottenham's team, playing in both the number 10 role and as one of the two midfielders that Spurs deploy in front of their defence.
In either position, the youngster has thrived and his sensational form has seen him called up to Roy Hodgson's latest England squad.
Alli was named in the Three Lions ranks which will face Lithuania and Estonia this month in Euro 2016 qualifying, capping off his rapid rise to the very top of the game.