Police responded to 64-06 Myrtle Avenue and found the child who suffered from injuries indicative of falling from an elevated position, police said.
The child was unconscious and lying on the ground when first responders arrived, witnesses said.
The child was taken to Cohen Children's Medical Center, where she's expected to recover.
Family members of the baby were emotional upon learning of what happened.
Detectives are speaking to witnesses and looking at security cameras, trying to piece together what exactly happened.
"I don't know I just received a call from my sister-in-law. And she told me something happened," the child's aunt said.
"I looked and I saw the girl there. She was prone, unconscious and there was a lot of people around her giving her aid and I just went back inside the office. Very upsetting and very depressing. And wondering what's going on, where the parents were. It was just very upsetting," a witness said.
It's unclear where her parents were at the time or how the child fell out of the window.
The investigation is ongoing.