The 21-year-old midfielder has linked up with the Rams until the end of the season, despite interest from other clubs.
"There were a few options but I had my mind and heart set on Derby," he is quoted as saying by Clubcall. "I have been keeping an eye on the results and the way things have been going. The lads are flying at the moment and hopefully I can come in and contribute to that."
Thorne has also experienced spells on loan at Portsmouth, Peterborough United and Watford.