Brendan had been a pro dancer on the show for the past 14 years.
He was one of only two original dancers left on the BBC One series up until 2017, along with Anton Du Beke.
But Brendan revealed his contract had not been renewed during a chat on ITV's Lorraine today.
"They've made an editorial decision not to have me back on the show," he said. "I'm in shock. I got a phone call. I've had 15 incredible series."
Brendan admitted: "I'm disappointed. I've always known this day would come. I'm a very strong character, some don't like that.
"I've never been contracted for more than one year. I still wanted to be part of it. My passion is still very much there."
The BBC said in a statement: "We'd like to thank Brendan Cole for being part of the show since the beginning - winner of the first series - and for the contribution he has made to its success.
"We wish him all the very best for the future."
Long time fans of Strictly have not been left impressed by the decision.
"Why are you doing this @bbcstrictly ? I love the show and have watched it since the start but @BrendanCole is the best!" one wrote.
Another posted: "Disgraceful! @BrendanCole is a massive part of Strictly! The show will not be the same without him. Shame on you BBC ☹️"
A third agreed: "Big mistake. Brendan was the heart of SCD. Such a character and a talented dancer and choreographer. Won’t be the same without him. "
"Bad decision. Characters like Brendan are what make the show more entertaining," added a fourth in response to a posting on the official Strictly Twitter feed.
As yet the rest of the pro line up for Strictly 2018 hasn't been confirmed.
Strictly Come Dancing returns to BBC One in the autumn.