Hunt has been nominated for an Academy Award for her portrayal of Cheryl Cohen-Greene, a real-life "sex surrogate" who is hired to sleep with a paralysed virgin.
She has previously appeared naked onscreen in 1992's The Waterdance, but she admits audiences see a lot more of her in The Sessions - and the prospect terrified her.
The Oscar winner tells British magazine Radar, "My vagina has never been in a movie (before), if we're going to go there... I certainly was not super-human and without any nerves about feeling exposed or judged for being a naked person.
"But whatever fears I had were smaller than my desire to be in it."
Hunt felt honoured to play Cohen-Greene, who she calls a "rock star" for her work as a clinical sexologist.
She adds, "I called her and said, 'It's Helen Hunt, could we speak?' She said, 'Great, I'm just getting out of the shower, then I have a client and I'll call you in two hours'. I hung up and went, 'Wait a minute, what? She's still doing this?' That told me something... She says she's gone to seminars and people are yelling out, 'W**re!'"