Malone has joined the 'Rams' for an undisclosed fee and has signed a three-year deal at Pride Park.
The left-back becomes manager Frank Lampard's eighth summer signing at Derby, who kicked off their season with a 2-1 win away at Reading on Friday night.
Lampard told the club's website: "Scott Malone is a player that I have liked for a long time and we're really pleased to bring him to Derby County.
"He's an attacking left-back with lots of speed and with the way we want to play, the full-backs are very important for us.
"I have spoken before about it being important to have options across all areas and Scott provides another one for us, but I think it's also important to mention that Max Lowe has been fantastic in the games so far," Lampard added.
August 8, 2018