The country's fourth leader since the end of apartheid in 1994, Zuma faces the task of guiding Africa's biggest economy, which may already be in recession, through the global financial crisis.
He will be inaugurated on Saturday and is expected to name his cabinet the following day.
Zuma has said he will consult widely with other ANC leaders before making major policy decisions, an approach that may ease opposition fears that the party will not tolerate dissent and will hurt South Africa's democratic credentials.
The ANC secured 65.9 per cent of the vote in the April 22 elections, equivalent to 264 seats in the country's 400-seat parliament.
But the tally was short of a two-third majority that would have given the ruling party a free hand to amend the constitution, marking the first time its support has declined since 1994.
Two other parties, the main opposition Democratic Alliance and the Congress of the People formed by ANC dissidents, won 30 and 67 seats in the national legislature respectively.