But three-time prime minister Sher Bahadur Deuba, who comes from the same social democratic tradition as Koirala, is seen as the frontrunner to take over the party which has had traditionally close ties with India, media reports said.
Two other main candidates in the fray are NC vice-president Ramchandra Poudyal and general-secretary Krishna Sitaula. However, Sujata Koirala, daughter of late prime minister Girija Prasad Koirala, has also announced to contest for the top post though without forming her team.
The four-day meet has been convened just three weeks after the death of Koirala, a moderate figure in the country's troubled politics, who died of pneumonia on February 9.
Koirala had a balanced view about India and his death presented a succession problem for the Koirala dynasty.
The party will also elect new central executive committee and present its political document during the convention.
Shashanka Koirala, son of the late popular leader BP Koirala, Arjun Narsingh K C and youth leader Gagan Thapa are vying for the second-important post of general secretary from the teams of Poudyal, Deuba and Sitaula respectively.
Among 85 members of the central committee, 65 including president, general secretary and treasurer are directly elected from among 3,100 general convention members.
(Reopens FGN 27)
The convention begins with a public meeting and top party leaders addressing the meeting, followed by a closed session on Friday. During that session, party's central committee will present policy and programmes, general secretary's report as well as financial report will be presented.
The convention is likely to amend the party statute to reform its structure and make the party more inclusive and democratic. Various foreign leaders have been invited for the inugural ceremony.
Bihar Chief Minister Nitish Kumar, BJP vice-president Bhagat Singh Koshiyari and general secretary of Socialist International Luis Ayala will attend the inaugural ceremony.
Nepal has been in turmoil since the new constitution was adopted in September. The Madhesi community, which has close ties to India launched protests against the charter, saying it did not address their demand for a greater say in government.
The popular Nepali Congress has some 600,000 members. It led the Peoples Movement of 2006 that after years of conflict abolished the 239-year-old monarchy.
However, NC pursues the ideology of democratic socialism and is known for its centrist policies.