The Rams released a statement last night confirming Simpson’s impending departure after two years as first team coach at the iPro Stadium.
The 48-year-old, who worked under McClaren during his spell in charge at Derby, will now be reunited with the former England boss at St James’s Park.
The statement said: “Derby County wishes to this evening announce that Paul Simpson will depart from the club’s employment from 1st July 2015.
“Simpson took up the position of first team coach in September 2013 following the arrival of Steve McClaren.”