Kahf, a Syrian-origin family law and immigration attorney from the township of Wayne, took the oath of office on Thursday with her hand on a copy of the Quran, the Muslim holy book, according to local news website North Jersey.
She will serve as a Passaic County Superior Court judge after New Jersey's Governor Phil Murphy nominated her a year ago, according to local media.
Though Kahf is not the first Muslim woman to serve as a state judge, she is the first to wear a hijab on the bench.
Since 2003, she has sat on the board of the New Jersey chapter of the Council on American-Islamic Relations, a Muslim civil rights organization where Kahf now serves as chairwoman.
She is also the legal adviser to Wafa House, a nonprofit domestic violence and social services agency based in the city of Clifton, and chairwoman of the Islamic Center of Passaic County.