The Oscar winner plays a desperate mum trying to survive a horrific apocalyptic event in the film, which became an international hit over Christmas, and she took on the role of Malorie after her adopted son Louis asked her to make more movies for him.
Bullock's kids were on set throughout the shoot, but they'll have to wait a while to see their blindfolded mum in action in the film.
"The reason I made "Bird Box" is my son kept saying, 'Why don't you make something for us'," Sandra said during a recent SAG Conversations interview. "This is the ultimate love letter to your kids, but they can't see this until they're a lot older."
"I had to ask myself, 'If these (movie kids) were my children, would I cut myself off so much from them emotionally in order to keep them alive?' The answer is yes, but I've never had to do that. My nine-year-old little boy shouldn't see this film now. He should wait."
The film has stirred up a lot of positive feedback with Chrissy Teigen applauding Sandra and director Susanne Bier for keeping her up at night over Christmas with strange dreams, and the actress is glad she signed on for a role, in which she's blindfolded for much of the action.
And she really committed to playing a sightless mum: "The second half of this film I was completely blind," she explains. "I had them make the blindfold but when I had the children I had them take out one layer, so I could see outlines of things because I would never want to put their lives at risk in the scene."
"I worked with an expert who was not sighted, who literally told me how to see things with my ears."