Poonam signed the membership form at the city BJP office in the presence of Rahul, uncle and senior party leader Gopinath Munde and state unit president Nitin Gadkari.
"I will work towards fulfilling my father's legacy as he felt very strongly about educational and women's issues. I am just an ordinary worker and will follow whatever orders the party gives," Poonam told reporters.
She parried a question on why she had been inducted in the BJP ahead of Rahul, saying, "My entry into politics was not accidental."
"I have planned to take the membership since a long time and had been doing social work for some time but there are some limitations. In politics, there will be no limits to what I can do," Poonam said.
Rahul expressed happiness over his sister's inclusion in the party saying, "I wish her all the best. We are one, it does not make a difference who joins the party, she or me. The BJP is in our blood and I would continue to work for it".
Asked when he would be joining the BJP, Rahul, who was embroiled in a drug abuse case, said, "Joining the party is a mere formality. It will be just a matter of time."
Munde also seconded his opinion saying Poonam's entry into the party is a collective decision taken by the family, including Rahul.
Rahul has decided that he wants to take some time before he joins BJP, the senior BJP leader said.
Dressed in a light green salvar kameez, Poonam appeared calm and relaxed as she chatted with party workers and accepted congratulations from them.
On the relations between BJP and Shiv Sena, Poonam said, "I am very close to the Sena and Balasaheb Thackeray, and I feel that with the efforts of our leaders like Mundeji and Gadkariji the alliance is going in the right direction."
"With the entry of Poonam, we have now a very good worker to work with the youth and women. She has Pramod Mahajan's blood in her veins and I am confident that she will do well," Gadkari told reporters.