Prime Minister Narendra Modi and other leaders of India's ruling party attended a ceremony in the Uttar Pradesh state capital of Lucknow, where Yogi Adityanath took the oath of office.
Adityanath is a five-time member of Parliament who has offended many in the country with his polarizing statements attacking the Muslim community.
The 44-year-old Adityanath has won the parliamentary seat from Gorakhpur district in Uttar Pradesh since 1998. He is also the head priest of a temple in Gorakhpur.
Two deputy chief ministers and 47 other ministers were also sworn in at the ceremony, which came a week after the ruling Bharatiya Janata Party won a landslide victory in state assembly elections.
Adityanath's anti-Muslim rhetoric has raised concerns among Uttar Pradesh's Muslims, who form nearly a fifth of the state's population.
On Sunday, Adityanath tried to reassure Uttar Pradesh citizens that his top priorities were good governance and development of the state, among the poorest in India.