Everton boss Moyes key in Irvine's Preston switch
Moyes has retained close links with the Deepdale outfit since he left for the Premiership five years ago.
Scot Irvine, 49, has waited 15 years for a management chance having also coached at Blackburn and Newcastle.
He said: "David is a very honest man and was terrific about it - I can't thank him enough.
"He spoke in glowing terms about Preston and didn't have a bad word to say about them.
"He felt it was a great opportunity for me."
After missing the play-offs by one place last season, Preston are now struggling fourth from bottom of the Championship.
Boss Paul Simpson was dismissed last week.