Uddhav Thackeray's wife Rashmi Thackeray was also present.
Sena leader and party's MP Sanjay Raut had said on Monday that Urmila Matondkar may join the ranks of the Shiv Sena on December 1.
"She (Urmila Matondkar) may join Shiv Sena tomorrow. She is a Shivsainik. We are happy that she is joining the Shiv Sena. This will strengthen the party's 'mahila aghadi'," Raut told reporters earlier.
Matondkar had last year resigned from the Congress party, a key ally of the Shiv Sena-led Maha Vikas Aghadi government in Maharashtra.
Matondkar had unsuccessfully contested the 2019 Lok Sabha election from the Mumbai North constituency and resigned from the party in September last year citing inaction on the part of "key functionaries of Mumbai Congress".