The Xena: Warrior Princess star was offered a pubic wig for her first full-frontal nude scenes - but, with one co-star keen to display all onscreen, she admits the pressure's on to go au naturale.
She says, "I haven't worn it yet... I was like 'have you got a red one?' We have one just in case.
"We have one person in the cast who insists on being naked... I think that person thinks it will surprise the person they're acting opposite.
Lawless plays Lucretia in the period epic, which will hit U.S. TV screens early next year (10), and performs her first full-on sex scenes with British actor John Hannah, who she insists was the perfect co-star.
She tells EW.com, "I couldn't have had a better partner... You have to make the unsexy look incredibly sexy.
But the actress insists the sex scenes were anything but pleasant: "It's the first time I had to do a sex scene; I try to think of myself as a modern woman but, honestly, I went home and had to go straight to bed. It was so stressful.
And she insists Spartacus will be a must-watch for lusty women as the newcomer, Andy Whitfield, has a terrific body, which he shows off in the mini-series.
She adds, "There's full frontal male nudity. You see plenty, trust me. I'm a little traumatised.".