The midfielder and Didier Drogba have both previously worked with the Portuguese at Inter and Chelsea respectively, with the Netherlands international viewing that as an advantage
The Dutchman, along with fellow Gala stars Dider Drogba and Hamit Altintop have all played under the Portuguese during the course of their careers.
They will be reunited with their old boss in the last 16 of the Champions League and Sneijder is confident of pulling off an upset.
"Mourinho knows us well and that is an advantage but the same applies for us," he is quoted as saying by Sky Sports.
"We know Mourinho very well, perhaps better than the Chelsea players know us. Chelsea is a great side, everybody has to accept that, but if we show the same spirit we did against Juventus, we could achieve another big result.
The way our fans support us when we're on the pitch is a driving force which pushes us to give our best. They are like the 12th man. Our strength is that all our players have very powerful characters.
"If we really put our heart into what we do and reflect all our quality into the game, play with our strength of character, then there isn't a single team we can't beat."
Galatasaray knocked Juve out of the Champions League in the group stage thanks to a dramatic 1-0 win over Antonio Conte's side in Istanbul.