However, the celebrations were marred as controversy erupted over the presence of Jagdish Tytler, an accused in the 1984 anti-Sikh riots, at the event.
Three new working presidents -- Devender Yadav, Haroon Yusuf and Rajesh Lilothia -- also took charge along with Dikshit.
The enthused workers greeted the former Delhi chief minister as she reached the office at DDU Marg with slogans and drum beats. Chants like "Sheila Dikshit Ayi Hai, Badlaw Ki Andhi Layi Hai" "(Sheila Dikshit has come with a storm of change) were heard.
With Dikshit at the helm of affairs, the party is looking to revive its fortunes in the national capital after a series of poll debacles starting with losing of power in 2013.
Dikshit said she will take the party to new heights in Delhi where it will replace all and sought help of ground-level workers. She also said the Congress will make full efforts to win all the seven Lok Sabha seats in Delhi.
Dikshit, 80, was appointed to the post by the party's national president Rahul Gandhi after Ajay Maken stepped down citing health troubles.
Senior Congress leaders Karan Singh, Janardan Dwivedi, Meira Kumar, PC Chacko, Sandip Dikshit and Ajay Maken were among those present as Dikshit took charge.