Two deputy chief ministers Keshav Prasad Maurya and Dinesh Sharma were also administered oath by Chairman of the Legislative Council Ramesh Yadav at a function at the Tilak Hall of the imposing Legislative Building here.
Two other ministers Swantradev Singh and Mohsin Raza also took oath.
Raza, a minister of state, is the lone Muslim face of the 48-member council of ministers headed by the 45-year-old saffron-robed chief minister.
Adityanath has now becomes the third successive chief minister after Akhilesh Yadav (SP) and Mayawati (BSP), to opt for the Upper House.
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With all the five seats going to the BJP, the party's tally has risen to 13 in the 100-member Upper House, where the Opposition still enjoys majority.
The Samajwadi Party (SP) has 61 members in the Legislative Council, the Bahujan Samaj Party (BSP) nine, the Congress two and the Rashtriya Lok Dal (RLD) one. While 12 seats are held by 'others', two are vacant.
The seats fell vacant when Bukkal Nawab, Yashwant, Sarojini Agarwal and Ashok Bajpai - all members of the Samajwadi Party - and BSP MLC Thakur Jaiveer Singh resigned and joined BJP subsequently.
Other UP chief ministers who had opted for the Legislative Council route are Narain Dutt Tiwari and late Ram Prakash Gupta (BJP).
Former chief minister Vishwanath Pratap Singh had become a member of UP Legislative Council in November 1980 after assuming the chief minister's office in June 1980.
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