Champion Whittaker was supposed to defend his belt against Luke Rockhold at UFC 221 in Perth but was forced to withdraw due to injuries.
Romero stepped up to fight Rockhold for the interim title and won with a massive third-round knockout, however, was ineligible for the title as he missed weight.
Despite missing weight, UFC officials said Romero would still be next in line to fight middleweight champion Whittaker.
In their previous fight at UFC 213 in July 2017, Whittaker claimed the interim title with a decision win over Romero.
Whittaker was then promoted to undisputed champion after Georges St-Pierre vacated the title.
The fight has yet to be confirmed by UFC but is expected to be the main event on the card.
There are also rumours circulating that CM Punk will make his return to the Octagon in his hometown of Chicago.
The UFC 225 fight card includes:
- Robert Whittaker vs. Yoel Romero
- Carla Esparza vs. Claudia Gadelha
- Joseph Benavidez vs. Sergio Pettis
- Curtis Blaydes vs. Alistair Overeem
- Rashad Evans vs. Anthony Smith
- Rashad Coulter vs. Allen Crowder
- CM Punk vs. TBA