The child fell from a window at East 167th Street and Washington Avenue just before 11 a.m.
He was taken to Harlem Hospital and was said to be stable.
It is believed the child climbed out the window that did not have bars.
A witness told Eyewitness News he heard a thud.
"It was only when I actually opened the door and saw him lying there that it hit me, that's when he let out a scream; I grew even more nervous, and-seeing him there-I didn't dare move him," said witness Jesus Toribo.
Toribo says he ran to the fire station on the corner for help.
"I didn't know what to do; I kept going back and forth to check on him until the firefighters finally arrived," Toribo said. "I stayed right there near him. I was a nervous wreck; my knees were shaking. It was terrible."
Officials say a parent was home at the time of the incident.
Few other details were released.
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