Wheatley moves to the Bantams on-loan to the end of the season.
The United striker returned from a similar spell with Northampton Town in January and has agreed a fresh switch, away from Old Trafford.
Wheatley said: “I am buzzing. We have been in discussions for quite a while, and I am excited to get the deal done and hopefully help the lads for the rest of the season.
“I hope I can add to the side after the strong start they have made and score goals. The last couple of months at Northampton, I grew as a player, and I want to continue doing that here.”
Bantams boss Graham Alexander added: “We are delighted to bring Ethan in to bolster our attacking options. He has fantastic attributes for a forward player, with plenty of League One games under his belt this season already.
“He showed a great desire to join us when we spoke, and I believe he is going to enjoy his time with us.”