Umaru Yar'Adua's election was widely condemned
Four members from his predecessor's administration have been given key positions, suggesting Olusegun Obasanjo will still be influential.
In the new line-up, the president will double as energy minister just like Mr Obasanjo did before him.
This will make Mr Yar'Adua responsible for Nigeria's petroleum industry and its troubled power sector.
Some leaders of the governing People's Democratic Party (PDP) have also been rewarded with key ministerial jobs, ostensibly, for their roles in the party's landslide win in April's polls.
The 32 men and seven women have been sworn in a ceremony in the capital, Abuja.
The delay in the announcement has impacted badly on government activities.
Political analyst Malam Mahmud Jega told the BBC the main tasks for the new ministers will be fighting corruption, improving security and efficiency.
Mr Jega, Nigeria's Daily Trust newspaper editor, said that "reforming the electoral system of the country so that we are guaranteed better elections next time" was also another challenge.
The Nigerian constitution requires that at least one minister is appointed from each of the country's 36 states to ensure fair representation.
According to Abuja University political analyst Kabiru Mathu, the delay in announcing the cabinet was not surprising.
"He [Mr Yar'Adua] is not a man to be rushed into taking sensitive decisions," he told the BBC's Network Africa programme.
The list of ministers also includes some opposition figures, apparently backing up Mr Yar'Adua's promise to form a unity government.
A key challenge for Mr Yar'Adua's government is fixing Nigeria's power sector to ensure constant supplies of electricity across the country. Often businesses rely on generators.
Nigeria currently generates about 2,500 megawatts of electricity compared to the 20,000 megawatts experts say is needed for the country to enjoy stable power supply.
Already, the new president has been saying the right things about sorting it out.
But critics point out that his predecessor started out in a similar fashion in 1999 - but failed to deliver during his eight years in power.
Mr Yar'Adua's governing PDP won a landslide victory in April's elections, according to official results.
Local and foreign observers said the elections were heavily flawed.
Although the opposition parties initially rejected the election results and filed cases in court to challenge the outcome, some backed down when Mr Yar'Adua promised them positions in a government of national unity.
Two leading opposition presidential candidates in the polls, former Vice-President Atiku Abubakar and former military leader Muhammadu Buhari, are pushing ahead with their court cases against Mr Yar'Adua's election.However, many of their followers have left them to take up jobs in the new PDP government.