According to TV Line, the actor has landed a "major arc" in the new episodes.
However, details of Hanks's character and storyline in the season are currently being kept under wraps.
Hanks recently starred in The Good Guys, which was cancelled in December. He has also had roles in shows such as Numb3rs, Mad Men, Band of Brothers and Roswell.
The president of Dexter's network Showtime recently revealed that the new season will go back to its roots but added that it will not feature one "big bad".
Dexter, which was renewed in December, is scheduled to return to Showtime later this year.
Watch a teaser for the sixth season of Dexter below: