The Town actress is in the frame to play a "sexy scientist" in the third instalment of Marvel's superhero series, after Jessica had to drop out due to scheduling conflicts.
Rebecca, 29, is currently in talks about the part, reports Variety.
If she signs up she will join Robert Downey Jr and Gwyneth Paltrow, who are set to reprise their roles, as well as newcomers Guy Pearce and Sir Ben Kingsley.
Jessica announced her news on Facebook earlier this week.
She wrote: "Sorry to say that Iron Man 3 isn't going to work out. My schedule is jammed packed and I can't fit anything else in. The press announced my possible attachment far too soon. I know many of you wanted me to be involved, and I'm so sorry to disappoint you."
Production on Iron Man 3 starts this month and the movie is due to hit cinemas in 2013.