Bihar Governor Devanand Konwar took over the additional charge as governor of West Bengal with effect from Monday, an official said.
Konwar would be in-charge as the governor of the state in addition to his own duties till regular arrangements are made.
State Chief Minister Buddhadeb Bhattacharjee, legislative assembly Speaker Hasim Abdul Halim, Trinamool Congress' Leader of the Opposition in the state assembly Partha Chattopadhyay and many other dignitaries also attended the swearing-in ceremony.
"The programme continued for almost one hour this (Monday) evening. Calcutta High Court's Chief Justice Bhaskar Bhattacharya was present during the swearing-in occasion," a Raj Bhavan official said.
Former Governor Gopalkrishna Gandhi's term ended Dec 13. He left the office of the governor Monday afternoon.