The Congress' central election authority (CEA) handed him over the certificate of his elevation to the top post during a grand event held at the lawns of the All India Congress Committee (AICC) headquarters here.
47-year-old Rahul Gandhi was handed over the certificate in the presence of his mother and predecessor Sonia Gandhi, sister Priyanka Gandhi-Vadra and her husband Robert Vadra, former prime minister Manmohan Singh and other senior party leaders.
While handing over the certificate, CEA chairman Mullappally Ramachandran termed the moment as "historic".
Meanwhile, parts of Lutyens' Delhi were dotted with posters hailing Rahul Gandhi's ascension with some of them describing the development as the beginning of a New India.
Rahul Gandhi succeeds Sonia Gandhi, who led the party for the last 19 years.
Rahul Gandhi entered electoral politics in 2004. He was appointed as the party general secretary in 2007 and was elevated as its vice president in January 2013.