Notably, it is the seventh time when Nitish Kumar is being sworn in as Chief Minister of Bihar.
Union Home Minister Amit Shah and BJP President Jagat Prakash Nadda attended the oath-taking ceremony of JD(U) chief as the new Chief Minister of the state. BJP's Bihar in-charge Devendra Fadnavis also participated in the event.
Nitish Kumar's new deputies - BJP's Tarkishore Prasad and Renu Devi were also sworn in today.
The main opposition Rashtriya Janata Dal (RJD) boycotted the swearing-in ceremony stating the mandate was against the National Democratic Alliance (NDA).
In a tweet, the RJD said: "The RJD boycotts swearing-in ceremony. The mandate for change is against the NDA. The mandate has been changed on the state's directions. Ask the unemployed, farmers, contract workers and employed teachers of Bihar what is going on with them. The public is agitated by the fraud of the NDA. We are the public's representatives and stand with them."
Kumar, after meeting Governor Phagu Chauhan to stake claim to form NDA government in Bihar, had on Sunday announced that the oath-taking, as well as the swearing-in ceremony of the new cabinet, will be held at around 4.30 pm on Monday.
The leaders of the NDA legislature party, which had secured a victory in the recently-concluded election in Bihar, had on Sunday met to deliberate on selecting a leader to lead the party. It had named Kumar as the leader of the NDA legislature party thus paving the way for his return as chief minister for the fourth consecutive term. BJP's Tarkishore Prasad, the MLA from Bihar's Katihar, replaced Sushil Modi as his deputy.
He had served as the Chief Minister of the state for little over seven days in March 2000, after which he was elected in 2005 when he served a full term.
He was re-elected to power in November 2010, after which he served for four years before resigning, and had again taken oath as Chief Minister in February 2015. He was voted to power in the 2015 Assembly election as part of the 'Mahagathbandhan'.
However, after corruption allegations were levelled against his deputy Tejashwi Yadav in 2015, Nitish resigned only to be sworn in as Chief Minister merely 12 hours later joining hands with the BJP to form a government in the state.
The NDA has secured a 125-seat majority in the 243-seat strong Bihar Legislative Assembly of which BJP won on 74 seats, JD(U) on 43 while eight seats were won by two other NDA constituents. The RJD, on the other hand, emerged as the single-largest party with 75 seats while the Congress only won 19 of the 70 seats it had contested on.