Chiu says he had recent conversations with both outgoing Mayor Gavin Newsom and Harris, and thanked them for considering him for the position.
He tells ABC7 he believes he can best serve San Francisco by remaining as a Supervisor.
"The challenges ahead of us will require a new level of collaboration between our elected leaders," Chiu said.
Chiu is an attorney who worked as a prosecutor in the District Attorney's office in the 1990s.
Newsom is expected to make his selection for interim district attorney sometime Thursday, but has not said when he will announce his choice.