Sherratt will replace Gruff Rees in the role at the Liberty Stadium.
The 41-year-old already has a wealth of experience from spells at Worcester Warriors and Bristol before joining the Blues.
Last season he worked with Wales’ backs in their summer tour clashes with Tonga and Samoa.
Sherratt said: “The opportunity to join the Ospreys was really appealing to me and I’m looking forward to a new challenge at such a fantastic region.
“There’s a great deal of potential in the squad, with a good combination of experience and youth and some new faces coming in to improve and add competition in the squad.
“The prospect of working with these players and a great staff is one I’m really excited about.
“I was really sold on the ambition of the region and with hard work and a fresh outlook, I feel I can help realise that ambition. In the meantime my focus is firmly with the Cardiff Blues and finishing this season strongly.”
Confirming that Sherratt will be joining the back-room staff at the Ospreys next season, managing director, Andrew Millward, commented: “When Gruff confirmed his intention to move on for a new challenge, we were looking at adding someone to the coaching team who could bring a fresh outlook to our approach and Matt fits the bill.
“He is someone with an impressive reputation as an innovative thinker and a good tactical and technical appreciation of the game who will bring something different to our environment.
“He has lots of ideas about how he can help develop our attacking game, using the experience he has gained in both the club and international scene.
“We look forward to Matt joining up with us in the summer.”
