News of the bout was first reported by NBCSports.com.
Cruz (18-1-0) agreed to face Johnson just weeks after successfully defending his title against former WEC featherweight champion Urijah Faber. He beat Faber by unanimous decision on July 2.
"Cruz cemented his claim as one of the best pound-for-pound fighters in the sport with an exciting win over Faber at UFC 132," White said, according to NBCSports.com. "He beat the one guy who had beaten him -- he got the monkey off his back."
When Cruz steps in the cage against Johnson, he will be making the fourth defense of his 135-pound belt.
Johnson (9-1-0) earned the title shot after beating former bantamweight champ Miguel Torres by unanimous decision in a closely contested fight on May 28.
The win over Torres was Johnson's fourth in a row.
This will be the second time a UFC title fight will appear outside of pay-per-view TV. It will be broadcast on Versus.
Franklin McNeil covers mixed martial arts and boxing for ESPN.com. He appears regularly on 'MMA Live,' which airs on ESPN2. Follow him on Twitter at www.twitter.com/Franklin_McNeil