The 25-year-old has impressed in the north east since arriving from Sint-Truiden in 2010, establishing himself as one of the most promising keepers in Europe.
"It's a big club and when you arrive it's a big thing," Mignolet told liverpoolfc.com.
"I'm very pleased to be here and I'm looking forward to getting started. The first training [session] will be very early and I'll be happy to be there.
"I think it will be very special the first moment I step onto the pitch."
Mignolet is confident he can fit in with manager Brendan Rodgers' passing philosophy, which starts with the goalkeeper.
"Back in Belgium, the goalies always train to play with the ball at their feet," he added.
"We join in most of the time, playing more with our feet than with our hands. I'm used to this.
"I've spoken to him [Rodgers] a few times already and I'm very pleased. He is very ambitious, like I am.
"Let's hope we can win a lot of games and finish as high up the table as we can."