Manohar Lal Khattar took oath as the chief minister for the second time on Sunday and Dushyant Chautala was sworn-in as his deputy as the Bharatiya Janata Party formed the government with the help of the Jannayak Janta Party in Haryana.
Governor Satyadeo Narain Arya administered oath to them at a ceremony held at the Raj Bhavan on Diwali. Other ministers of the Khattar cabinet are expected to be sworn-in after a few days.
Former chief minister and Congress leader Bhupinder Singh Hooda, Shiromani Akali Dal chief Sukhbir Singh Badal, former Punjab chief minister Parkash Singh Badal and BJP working president J P Nadda were present on the occasion.
Dushyant Chautala's father Ajay Chautala, who stepped out of the Tihar jail in Delhi on a furlough, and mother Naina Chautala, who has been re-elected as an MLA, attended the event.
However, Indian National Lok Dal leader Abhay Singh Chautala, the estranged uncle of Dushyant Chautala, was not present.
Punjab Governor V P Singh Badnore, Union ministers Narendra Singh Tomar, Krishan Pal Gurjar, R L Kataria, Uttarakhand Chief Minister Trivendra Singh Rawat and his Himachal counterpart Jai Ram Thakur were also there at the ceremony.
The BJP had on Friday sealed a deal with the Dushyant Chautala-led JJP to form the government in Haryana after the saffron party fell short of six seats from the majority mark in the assembly election.
In the 90-member assembly, the BJP had won 40, JJP 10, Congress 3, INLD and the Haryana Lokhit Party one each, while seven Independents also won.
Both the 65-year-old Khattar and 31-year-old Dushyant Chautala took oath in Hindi. In their brief media interaction after the oath-taking function, the two leaders said the alliance would provide a stable government.
Dushyant Chautala, great grandson of former deputy prime minister Devi Lal, said the government would work towards the welfare of all sections of the society.
Ajay Chautala said he felt proud that "Today, I'm known in the public as Dushyant's father".
The former MP said it was hard to believe that Dushyant Chautala had built the party in just 10 months and some of its candidates even made stalwarts bite the dust.
"He (Dushyant) always consults me whenever he has to take any major decision," said Ajay Chautala, who is lodged in jail along his father and former chief minister Om Prakash Chautala after their conviction in a teachers' recruitment scam.
Asked about the Congress raising doubts about the prospects of the BJP-led coalition, Ajay Chautala said: "Whatever the Congress says, it's their wish. Definitely, this alliance will work and it will take forward the development work of Haryana in the next five years."
In 2014, Khattar became the state's first Punjabi-speaking chief minister and the first non-Jat leader to occupy the post after 18 years when Prime Minister Narendra Modi handpicked him.
Then aged 26, Dushyant became the youngest MP in 2014 when he was elected from Hisar by defeating Congress veteran Kuldeep Bishnoi.
Parkash Singh Badal also underlined that the BJP-JJP coalition would provide a stable government in Haryana.
Asked if Dushyant Chautala would carry forward the legacy of Devi Lal, Badal said: "Definitely, he will be able to do so. Chaudhary Devi Lal would have been very happy had he been alive."