Derby beat the transfer deadline to sign midfielder Bradley Johnson from Norwich.
A statement on the club’s Twitter feed, posted shortly after the 1800 BST cut-off point, revealed the 28-year-old’s arrival on a permanent, four-year contract.
Sky sources say the fee for the player, who was Norwich’s player of the year last season, is in the region of £6m.
Jacob Butterfield signed earlier on deadline-day, and the Johnson deal takes Derby’s tally of summer signings to nine.
Boss Paul Clement said: “Being able to bring Bradley to Derby represents a major coup for the football club.
“His experience will prove invaluable to us. He knows how to get out of this division and is a leader.”
Johnson twice won promotion during his four years at Carrow Road but started just one of four Premier League games under Alex Neil this season.