Governor Najma Heptulla administered the oath of office and secrecy to Singh at a function in Raj Bhavan here.
Eight other ministers from the BJP and its alliance partners also took oath along with the chief minister. Y Joykumar of NPP has been designated as the Deputy Chief Minister.
The other ministers are Th Biswajit Singh of BJP, L Jayantakumar Singh, L Haokip and N Kayisii of National People's Party, L Dikho of Naga People's Front and Karam Shyam of LJP.
Outgoing Chief Minister Ibobi Singh was also present.
BJP President Amit Shah and Union minister M Venkaiah Naidu, who were scheduled to attend the function, could not arrive here as the aircraft they were travelling in suffered an engine problem mid-air prompting the pilot to return to Delhi.
Heptulla had yesterday invited Biren Singh, who was unanimously elected the leader of the 21-member BJP Legislature Party, to form the government.
The BJP has claimed the support of 32 MLAs in the 60-member Assembly.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)