Alex Padilla has been named to replace Vice-President-elect Kamala Harris in the US Senate by California Governor Gavin Newsom, filling the remainder of her term in the upper house, BBC reported.
He is the first Latino to represent California in the house and a close ally of Mr Newsom.The son of Mexican immigrants, he became California's first Latino secretary of state in 2015.
He is due to hold the Senate seat until 2022 when Harris's term ends.
In a statement, Mr Padilla pledged to "work each and every day to honour that trust and deliver for all Californians".
"From those struggling to make ends meet to the small businesses fighting to keep their doors open to the health care workers looking for relief, please know that I am going to the Senate to fight for you. We will get through this pandemic together and rebuild our economy in a way that doesn't leave working families behind," he added.