AAP leader Guggan Singh, who was the party's candidate from northwest Delhi in the 2019 Lok Sabha polls, returned to BJP on Monday.
Mr Singh joined the BJP in the presence of Union Minister Prakash Javadekar and Delhi BJP Chief Manoj Tiwari, ahead of assembly polls in the national capital.
Mr Javadekar is also the BJP's assembly election in-charge in Delhi.
Guggan Singh had quit the BJP and had joined AAP in July 2017.
The Dalit leader was defeated by BJP's Hans Raj Hans by over 5.9 lakh votes in the Lok Sabha elections for the reserved seat. Previously, he was elected as MLA from Bawana in 2013 on a BJP ticket.