The Game of Thrones star said: "You hear about all your contemporaries getting it done and you're like, 'Does that mean I have to? Should I be doing that?' And then you work on a movie and the director of photography lights you beautifully and you get over it.
"I work in an industry where I've got to move my face, and I've got to be expressive, and you can't light filler. You just can't light it. It doesn't look right, you look shiny and strange. If my job is telling me that I need to have anything more than possibly a bit of botox when I'm 45 or whatever, then I'll stop doing the job."
And the 34-year-old actress - who also revealed she was told to get fillers by a facialist when she was just 28 - doesn't mind her "wiseness" and "intelligence" being reflected in her face.
Speaking to Elle UK magazine, she added: "You've got this idea of ageing, and then you've got the idea of what ageing makes you look like. At 34, I am wiser, more intelligent, I've had more experiences, I've done all this stuff and I'm proud of that. You can only do that because you are the age you are.
"Time is the only thing that allows you to do those things. So, if my face is gonna reflect the time that I've spent on this earth, I'm down for that ... My mother has never had any work done and I think she's incredibly beautiful. I look to women and actors who are older than me who are f****** beautiful and I think what your skin does as you age is elegant. I can imagine them all saying, 'Ssh, you do not get to talk about this yet', but I've got lines on my forehead."