"Riccardo was one of the driving forces on the pitch for Nottingham Forest last season," Adams told the clubs official website.
"He is a versatile player who can operate in a variety of positions in midfield or defence.
"I have consistently said that we need to bring in several new faces to the football club and we are delighted we can add Riccardo to that list.
"There is a lot of work going on behind the scenes and we are hopeful of making more new signings in the not too distant future," added the Foxes boss.
Scimeca becomes Adams' third close-season signing following the captures of Steve Howey and Paul Brooker.