Pettis replaces TJ Grant, who withdrew from the bout after suffering an injury.
"Thanks everyone for your concerns," Grant said on Twitter. "I am healing from a concussion I suffered in [Brazilian Jujitsu] of all things. I hope to be back training."
The Henderson-Pettis fight will be a rematch of their classic WEC title showdown in December 2010. Pettis won that fight by unanimous decision to lift the belt from Henderson.
The timing of the rematch could not have come at a better time for Pettis, who resides in Milwaukee. He was scheduled to face featherweight champion Jose Aldo in Rio de Janeiro on Aug. 3, but injured a knee while training and pulled out. Aldo now will defend his title against Chan Sung Jung.
Despite having never competed at featherweight, Pettis asked for and received the 145-pound title shot after former Strikeforce lightweight champion Gilbert Melendez was selected to face Henderson in April. Henderson defeated Melendez by split decision. Shortly thereafter, UFC officials announced that Grant and Gray Maynard would fight for the right to face Henderson in Milwaukee.
Grant defeated Maynard by first-round knockout to secure the title shot. Meanwhile, Pettis' knee began healing faster than expected and he asked UFC officials to let him fight Henderson. His request, however, was denied.
Landing a UFC title shot has proven difficult for Pettis since he joined the promotion in 2010. He was slated to fight the winner of then-lightweight champion Frankie Edgar and Maynard, but their January 2011 bout ended in a draw, putting Pettis' title shot on hold. Rather than remain idle, Pettis agreed to fight Clay Guida in June 2011, but he lost that fight by unanimous decision, which temporarily knocked him out the top contender spot.
Pettis (16-2) has won three fights in a row since the loss to Guida. He reclaimed the No. 1 contender position with a first-round knockout of Donald Cerrone on Jan. 26.