McIntosh, known as the Chief, reached legendary status during his playing days at Pontypridd and made 33 European appearances.
The 43-year-old coached Pontypridd to a first cup and league double in 2012/13 after securing a Principality Premiership League title in 2012 and a Swalec Cup victory in 2011.
He was already working with the Blues on a part-time basis but will join them permanently following this weekend's Pool Two clash with Toulon.
"Dale and I go back a long way from our playing days and I have huge respect for him as a man and rugby person," said Blues director of rugby Phil Davies.
"He has been a simply phenomenal servant for Pontypridd. They are a great club and, along with Cardiff RFC, are a great credit to our region.
"Dale has done a fantastic job for Pontpridd, as a player and coach, and has also been successful as part of the Wales Under-18 set-up. His pedigree as a rugby man, player and coach is outstanding.
"When I first arrived at Blues last year I wanted him involved. At that stage it wasn't possible, but over the course of the last 18 months we have kept in touch through his role in the region and he has been involved with us from the summer.
"We are very grateful to the WRU and Pontypridd for releasing him to become Defence Coach with us on a full-time basis.
"I would also like to thank Rob Powell for his contribution to Blues. He joined us to work alongside Xavier Rush last season and has continued to work hard for us this season. We wish him every success for the future."