BJP president Rajnath Singh announced Upadhyay's appointment on Tuesday night and said the appointment will come into effect immediately. (Agencies)
Upadhyay succeeded Harsh Vardhan, who had resigned from the post after being elected an MP from Chandni Chowk and elevated to the Union Cabinet.
His appointment comes at a time when suspense over the impending Delhi Assembly elections continue to loom large, with the BJP keeping the cards close to its chest with regard to its future strategy in the state.
"My priority is to strengthen the party and carry forward the mandate given to BJP by the people of this country," Upadhyay said on Tuesday.
"I will try to keep the organisation united and take every one along," he said.
Asked when the Assembly elections could be held in Delhi, he said, "I think it's too early to comment on it now. The national leadership will decide the future course of action."
BJP had won 31 seats in the 70-member Delhi Assembly in the last elections, falling short of a simple majority.
Arvind Kejriwal-led AAP, which won 28 seats, formed the government with outside support from Congress.
Kejriwal, however, resigned after 49 days in office, following which the Delhi Assembly continues to be in suspended animation. Delhi is now under the President's Rule.
BJP president Rajnath Singh announced Upadhyay's appointment on Tuesday night and said the appointment will come into effect immediately.