The Dutchman is playing his best football this season under the Portuguese.
Sneijder said: "Working with Mourinho is really something special. He loves his players and is very professional.
"The thing that distinguishes him the most is the intensity and the meticulousness of his work with every single player and the value that he assigns to the tiniest detail.
"Inter are without doubt among the six best teams in Europe. I have no doubt about this."
Finally, Sneijder reflected on his decision to join Inter in the summer.
"I like living here a lot. There are a load of restaurants and shops. And, apart from this, the people of Milan are very friendly.
"I feel very much in form at the moment. I think that I have adapted myself to Italy and the team in quite a hurry.
"But obviously there is always room for improvement."