He will join Garth Ennis, whose Red Team was the first series to be announced for the new line.
"It's not every day that a publisher offers you the chance to create a whole new world from scratch, and I'm having fun cooking up something dark, funny, violent and twisted for Dynamite," said Diggle.
"Hard-hitting genre fiction with a twist, for readers who don't like having their intelligence insulted. The kind of comic I want to read myself. So there's really just one question - are you in or are you out?"
The writer's title has yet to be revealed. Dynamite is promising a series of announcements still to follow.
Diggle has also been announced as the new writer on DC Comics' Action Comics, replacing outgoing scribe Grant Morrison.