The health ministry said 281 were now known to have died in the attack, which targeted a shopping complex in the mainly Shia Muslim Karrada district.
The previous death toll, announced by the ministry on Tuesday, was 250.
The jihadist group Islamic State (IS) has said it was behind the bombing, the deadliest in the country since the 2003 US-led invasion.
IS militants overran large parts of northern and western Iraq two years ago, but government forces have since regained much of the territory.
In response to the battlefield setbacks, including the recent loss of the western city of Falluja, the militants have stepped up their attacks on civilians.
In Sunday's bombing, an explosives-laden lorry blew up outside a crowded, three-storey shopping centre where people had been enjoying a night out after breaking their daily fast for the Islamic holy month of Ramadan.
On Thursday, the health ministry raised the death toll from the attack after more of those registered as missing were identified as dead, spokesman Ahmed al-Rudaini told the Reuters news agency.
Hospital and police officials told the Associated Press that the death toll might rise as human remains were still being recovered from the blast site.
More than 200 people were wounded in the attack, 23 of whom are still in hospital.
The bombing has sparked widespread anger among Iraqis, some of whom have accused the government of failing to protect them.
When Prime Minister Haider al-Abadi visited the bombing site, people threw stones and shoes at his convoy and called him a "thief".
On Tuesday, Interior Minister Mohammed al-Ghabban offered his resignation to Mr Abadi, conceding that the bomber had managed to pass through several security checkpoints on its way from the eastern province of Diyala to central Baghdad.
Mr Ghabban blamed a lack of communication between the multiple forces in charge of security, and called for the interior ministry to be given overall responsibility.
Mr Abadi accepted the minister's resignation on Wednesday, an official in his office told the AFP news agency, although there was no official announcement.
Iraqi officials have again raised the figure for the number of people killed in Sunday's suicide bombing in Baghdad.