The hooker from the British and Irish Lions is going to join Montpellier.
Over the course of 12 years, the 29-year-old has made 163 appearances for the Grecians and helped them win two English titles.
After the World Cup, he won't move to France.
Cowan-Dickie, who has won 42 England caps and played in all three Lions Tests against South Africa in 2021, will not be able to play for England after the tournament.
He told the club website he was sad to be leaving. I've been at the Chiefs for over a decade.
It was an opportunity that I had to think about a lot. It wasn't an easy decision to make, but I spoke to my family and they were in favor of it.
I hope I have plenty of years left in my career, but this is an opportunity for me to show what I'm all about.
The reduced level salary cap of $5m continues to take effect, and he is the latest big name to leave.
Sam Skinner and Tom O'Flaherty were two of the players who left last summer.
Jack Nowell and Dave Ewers are both out of contract in the summer and there are still questions over their futures.
Cowan-Dickie wants to go out on a high and win some silverware.
The most important year of my career is this one. I'm excited to get out there and put my best foot forward because the club, the people, the supporters have done so much for me.
It also means the end of an international career that began when he helped win the first ever junior World Cup for England.
After making his senior debut in a pre-World Cup game against France, he became a regular and helped England win a 2016 Six Nations Grand Slam.
He scored tries in all of England's pool games at the World Cup and came on as a replacement in the final.
He came on as a replacement in the final Test of the tour after scoring a try in the first Test.
It's difficult to leave that behind when you're playing for England.
Between now and the move, I hope I get more opportunities to give.
I would like to be involved in both the World Cup and the Six Nations.
I need to play well at club level in order to do that. I want to see what happens in the future.
The analysis is done byBrent Pilnick.
He has less years ahead of him than behind him, which is why he decided to leave.
While England's top clubs are constrained financially, the same is not the case across the Channel and Cowan-Dickie can't be blamed for wanting to secure some stability for himself and his family in the last years of his career.
There is a question of what will happen to a group of talented and influential home grown players like Cowan-Dickie, Nowell, Sam and Joe, who all start to enter their late 20's and early 30's.
A new generation of players will have to be drafted in to replace the ones who will end their time at Sandy Park one day.
There are exciting young players coming through, but it will be hard to replace the talent that has already left.