Terming the occasion as Modi's "Vijay Chai", members of the BJP youth wing set up a giant screen to show the hour-long oath-taking ceremony at the Rashtrapati Bhavan.
"Our members also set up a dozen stalls around the party office to serve tea to the public present on the occasion. Tea became a symbol of our party's stunning victory in the Lok Sabha election," youth wing president Saptagiri Gowda told IANS.
Modi is said to have assisted his father Damodardas Modi, who had a tea stall at the Vadnagar railway station in north Gujarat, about 100 km from Ahmedabad.
Earlier, about 100 members of the youth wing took part in a bike rally from Freedom Park in the city centre to the party office to mark the event.
The BJP used the beverage (tea) extensively during the poll campaign across the country to seek votes for Modi.
The party also celebrated the induction of former chief minister and Bangalore North Lok Sabha member D.V. Sadananda Gowda and six-time Lok Sabha member from Bangalore South Ananth Kumar as cabinet ministers and Davangere Lok Sabha member G.M. Siddeswara as minister of state.
About 40 leaders from the BJP state unit, including Shimoga Lok Sabha member B.S. Yeddyurappa and state unit president Jagadish Shettar, Dharwad Lok Sabha member Prahlad Joshi, former deputy chief minister K.S. Eshwarappa, and former state ministers C.T. Ravi, Govind Karjol and Arvind Limbavali flew to New Delhi to attend the oath-taking ceremony.