Governor Urmila Singh administered the oath of office to Virbhadra Singh, 78, who has been chief minister of the hill state for more than 16 years, at the historic Ridge.
The others who took oath were eight-time legislator Vidya Stokes, seven-time legislator Kaul Singh, G.S. Bali, Sujan Singh Pathania, Thakur Singh Bharmouri, Mukesh Aghnihotri, Sudhir Sharma, Parkash Chaudhary and Dhani Ran Shandil.
Outgoing BJP chief minister Prem Kumar Dhumal and his erstwhile cabinet colleagues were conspicuously absent from the ceremony.
There was also no minister from the Congress-led central government at the event.
Virbhadra Singh took oath at 10.40 a.m. as the state's 13th chief minister in the presence of thousands of supporters.
He first assumed office April 8, 1983, replacing Thakur Ram Lal.
Belonging to the erstwhile princely state of Rampur Bushahr, Virbhadra Singh entered politics at the age of 28.