Wilson Reyes had been accused of stealing $5 from a schoolmate. The boy's mother, Frances Mendez, claimed he did not take the money, according to the Associated Press.
Mendez told the New York Post her son was "interrogated" for hours on Dec. 4.
"My son was crying, `Mommy, it wasn't me! Mommy, it wasn't me!' I never imagined the cops could do that to a child. We're traumatized," Mendez told the AP.
The city dropped the robbery charge against Wilson on Dec. 26, the Post reported.
The Daily Mail obtained lawsuit documents that claim, "Reyes was handcuffed and verbally, physically and emotionally abused, intimidated, humiliated, embarrassed and defamed."
Deputy Commissioner Paul J. Browne told ABC News in an emailed statement the allegations against the police were false:
“While the lawyer’s claims are grossly untrue in many respects, including fabrication as to how long the child was held, the matter is nonetheless being reviewed by the department’s Internal Affairs Bureau.”