Sixty-year-old Khattar, the first-time MLA from Karnal assembly segment, took oath at Panchkula near here.
Jubilant party workers and supporters took to the streets in Karnal to celebrate. BJP workers and supporters burst crackers and distributed sweets among the residents.
Many residents hoped that Karnal would witness good development now as the area had allegedly remained ignored during the previous Congress regime.
The Prem Nagar locality where Khattar has been residing also became a centre of hectic activity.
Meanwhile, celebrations also took place at other places in Haryana including Sonepat, Ambala Cantt and Narnaund, the assembly constituencies of newly inducted ministers Kavita Jain, Anil Vij and Capt Abhimanyu.