The Captain Britain and MI13 writer will produce comics solely for the publisher for the next two years.
"I couldn't be happier, or feel more welcomed, in my new playground," wrote Cornell on his blog.
"Indeed, I'm a couple of issues into one title you haven't heard about yet."
Cornell's Lex Luthor-starring run on Action Comics alongside artist Pete Woods begins in issue #890 on June 30.
Luthor will be facing off against a who's who of assorted DC Universe villains in the run-up to the milestone 900th issue.
DC revealed that Superman's nemesis will encounter Vandal Savage, Larfleeze and feature in a crossover with the Secret Six.