In the tape, posted on a website often used by groups in Iraq, al-Zarqawi defended the blasts on three hotels saying al-Qaida had inside information that they were home to US, Israeli and Jordanian intelligence agencies.
"We ask God to have mercy on the Muslims, who we did not intend to target, even if they were in hotels which are centres of immorality," the voice on the tape said.
"The idea that they blew up inside wedding ceremonies is a lie by the Jordanian regime... The target was a meeting of intelligence agencies, but a roof collapsed on a wedding party from the blast," he said.
It was not possible to verify the tape.
The triple bombings killed 54 people in the Amman hotels, sparking outrage in Jordan. Most of the victims were Jordanians attending wedding parties.
Al-Qaida in Iraq is one of the main groups fighting against US forces and the US-backed government.
"We chose these hotels after over two months of thorough checks with trusted sources inside the hotels and elsewhere showed that they were centres for Jewish, US and Jordanian security apparatus," al-Zarqawi said.