Payton Gendron is charged with first-degree murder in connection to the shooting at a Tops supermarket.
Gendron appeared in court wearing a white smock. A public defender entered a not guilty plea on his behalf.
Gendron is due back in court on May 19 for a felony hearing.
Ten people were killed in the shooting. Three others were wounded and expected to survive.
The FBI is investigating the shooting as a racially-motivated attack and a hate crime. Authorities said 11 of the victims are Black. The other two are white.
This story was originally reported by August Erbacher on wkbw.com.