Shannon Morgan filed the suit on Thursday in federal court, saying the agency violated her First Amendment rights by rejecting a plate reading "8THEIST".
The Maurice River Township woman said plates reading "BAPTIST" have been approved.
Messages and e-mails left for the Motor Vehicles Commission were not immediately returned. A recorded message said the offices were closed in observance of Good Friday.
New Jersey previously approved a request from a national atheist group's president for a license plate with the word "atheist" after a brief flap. His plate had the number "1" in place of the letter "i".