Evan Sachs pleaded not guilty Friday to charges of attempted murder, assault and weapons possession.
Sachs was arrested in October after he allegedly attacked and nearly killed the boy at a Dave and Busters in Westbury.
The boy, who has not been identified, has since recovered.
Police say Sachs, a 23-year-old movie theater usher, had been stalking potential victims at area malls. He was arrested moments after the stabbing.
Attorney Eric Sachs, who is not related to the defendant, says his client was being treated for a psychiatric disorder when the stabbing occurred.
Evan Sachs is being held without bail. He is due back in court Dec. 7.