A US official told the Associated Press no consular staff or guards were hurt in Friday's blast.
But the city's leader told Reuters news agency one person was killed and five wounded.
"It seems the consulate was the target," said Mayor Nihad Qoja.
The explosion came as a series of bombings hit public places in the Iraqi capital Baghdad, killing at least 29 people.
No one immediately claimed responsibility for Friday's attacks.
Irbil, in Iraqi Kurdistan, is widely seen as the most secure part in the strife-torn country.
But the semi-autonomous region is a key partner in the US-led fight against the Islamic State group.
Helped by air strikes, the Kurdish peshmerga paramilitary have driven back the extremist militants.