Rawat, 56, along with nine ministers -- seven of Cabinet rank and two Ministers of State --was administered the oath of office by Governor Krishna Kant Paul here in the presence of Prime Minister Narendra Modi and Bharatiya Janata Party President Amit Shah.
Union Ministers Rajnath Singh, J.P. Nadda and Uma Bharti, and former Congress Chief Minister Harish Rawat were also present.
Incidentally, the majority of state Cabinet members are leaders who moved from the Congress to the Bharatiya Janata Party (BJP).
The Cabinet Ministers are Satpal Maharaj, Madan Kaushik, Yashpal Arya, Harak Singh Rawat, Prakash Pant, Subodh Uniyal and Praveen Pandey.
Dhan Singh Rawat and Rekha Arya are Ministers of State.
While Harak Singh Rawat, Yashpal Arya, Subodh Uniyal and Rekha Arya joined the BJP before the February 15 assembly elections, Satpal Maharaj joined the party in 2014.
Trivendra Rawat is the fifth Bharatiya Janata Party Chief Minister of the hill state after it was carved out of Uttar Pradesh in 2000.
Trivendra Rawat was elected leader of the BJP legislature party on Friday after the party won a landslide majority in the assembly elections, winning 57 of the 70 seats. The Congress got 11.
Both Modi and Shah exuded confidence that the Rawat government will usher in development in the state.
"The new Uttarakhand government will return the tremendous affection shown by the state's people with record development," said Modi.
"I firmly believe this BJP government will take the pro-people policies of the Modi government to every door in the state and set up new standards in progress and development of the state," said Shah.
Holding a postgraduate degree in history and a diploma in journalism, Rawat joined the RSS as a 19-year-old student in 1979. He steadily rose up the ranks. Before heading its Dehradun unit he served as a pracharak (campaigner) in the 1990s.
He was made BJP General Secretary (Organisation) of an undivided Uttar Pradesh in 1997 and was instrumental in building the party cadre in Garhwal and Kumaon regions of present-day Uttarakhand that was formed in 2000.
Rawat had his share of controversies in government and politics. He was name in the multi-crore rupee "seed scam" in the Agriculture Department.
Elected from Doiwala seat by an over 24,000 vote margin against Congress rival Hira Singh Bisht, the new Chief Minister is widely regarded in the party for his organisational skills.
The party formed its first government in the state in 2000 when Nityanand Swami was the first Chief Minister.
(Brajendra Nath Singh can be contacted at email@example.com )