Haryana Chief Minister Nayab Singh Saini was administered oath of legislator by the Assembly Speaker on Thursday here.
Speaker Gian Chand Gupta administered the oath to the BJP leader in his chamber.
Mr. Saini recently defeated his main rival, Congress's Tarlochan Singh to win the bypoll for the Karnal Assembly seat, which was earlier held by party colleague Manohar Lal Khattar.
In the 2019 Assembly polls, Mr. Khattar had retained the seat defeating Tarlochan Singh.
Mr. Saini, the outgoing MP from Kurukshetra, had contested the by-election for the Karnal assembly seat after he replaced Khattar as chief minister.
The bypoll was necessitated by Mr. Khattar's resignation as MLA from Karnal after his removal from the post of chief minister.
Polling for the state's 10 Lok Sabha seats and the Karnal assembly constituency was held in the sixth phase of the general election on May 25 and the results were declared on June 4.
Mr. Saini was sworn in as the chief minister on March 12.
Mr. Khattar, who was fielded by the BJP from the Karnal parliamentary segment, won the seat.
