Sena President Uddhav Thackeray and other senior leaders welcomed him into the party fold by tying a red thread symbolizing 'Shiv Bandhan' and handing him a miniature party flag.
Speaking on the occasion, Kshirsagar said that he felt "suffocated" in the NCP and criticized party President Sharad Pawar for the circumstances leading to his crossing over to the Shiv Sena.
Thackeray said the Sena would be further strengthened in Beed and Marathwada region with the entry of a senior and experienced leader like Kshirsagar.
However, the Sena chief refused to reveal details of the National Democratic Alliance (NDA) dinner meeting in New Delhi on Tuesday.
Thackeray also refused to comment on the recent exit poll projections predicting a huge win for the Bharatiya Janata Party (BJP) and NDA, nor speculated on the probable outcome as the vote count for the seven-phased elections will be taken up on Thursday.
Earlier on Wednesday, Kshirsagar tendered his resignation from the NCP and also as a legislator from Beed.
During the erstwhile Congress-NCP government he served as a minister handling various portfolios.
However, since the past couple of years, he was upset at being 'sidelined' by his nephew Sandip Kshirsagar and Leader of Opposition (Council) Dhananjay Munde in Beed and regional politics.
He had fuelled speculation over joining the BJP after Chief Minister Devendra Fadnavis visited his home in 2018 along with Minister Pankaja Munde, the cousin of Dhananjay Munde, and had once shared a public platform with the Chief Minister.
In the 2019 Lok Sabha elections, Kshirsagar earned the NCP's ire after he openly campaigned for the BJP candidate Pritam Munde against the NCP's nominee Bajrang Sonavane, on account of intra-party political rivalry.
Reacting to the development, Dhananjay Munde said that Kshirsagar's plans to quit the NCP were in the air for long, "so what is the reason for the 'muhurat' taking place today", on the eve of the vote count in the parliamentary elections.
( With inputs from IANS )