47-year-old Mukul, who led the Congress to a spectacular victory with 29 seats in the 60-member Assembly, just two short of a simple majority, became the chief minister for the second straight term.
He was administered the oath of office by Governor Ranjit Sekhar Mooshahary.
Speaking to reporters after the swearing-in ceremony, Sangma said, "Our focus will only be on development, development and development because the people of the state deserve it. It will be our sincere commitment...That whatever promises we have made shall be implemented in letter and spirit."
Apart from 29 Congress MLAs, eight Independent candidates have assured of 'unconditional' support in the government formation. So has the NCP which has won two seats.
According to a top Congress functionary, Sangma has already finalised the list of ministers in consultation with AICC president Sonia Gandhi in New Delhi.