One car bomb hit Baladiyat in eastern Baghdad, killing at least 13 people, security and medical officials said.
A second struck Adhamiyah in the north, killing at least five, and a third, in the central Karrada district, left at least five more dead.
The bombings also wounded more than 50 people.
Militants led by the powerful Islamic State jihadist group have seized large areas of Iraq since June, and Iraqi security forces are still struggling to regain ground.
Bombings in and around Baghdad killed at least 26 people Thursday, while a suicide car bomb on Tuesday killed 28 people, among them an MP who was also a senior Shiite militia commander.