Portman stars as the ambitious Anne Boleyn, who became Henry's second wife and eventually was executed. Johansson plays her little-known older sister, Mary, who was Henry VIII's mistress before her sister married the king (played by Eric Bana).
The stars said they were helped by the costumes from designer Sandy Powell, who won Oscars for her work on "Shakespeare in Love" and "The Aviator."
"It wasn't like I went to set every morning ... and was like, I can't wait to be corseted," Johansson told reporters. "But the costumes really aided in a way - they were kind of characters in themselves."
The outfits provided "a constant reminder of the restrictions placed on women at the time," she said. "You can't even move your arms, and everything is very statuesque and you have this giant skirt around you, and it's interesting how that changes the way you interact."
Portman said the costumes were "definitely helpful in creating the characters" and argued that the figures' story and emotions remain relevant to the modern world.
"Human emotion doesn't change," she said. "I think that's one of the hard things for us to imagine - how history might have been sexy, gossipy, glamorous."