After his release on Tuesday he told journalists: "I am free again, but my homeland is still a prison."
Reuters news agency reported he was slurring his speech because of a missing tooth.
He went on to say he had suffered beatings, whippings, electric shocks and simulated drowning at the hands of officials and guards.
"At the time that Prime Minister Nouri Maliki said on television that he could not sleep without being reassured on my fate... I was being tortured in the worst ways, beaten with electric cables and iron bars," he said.
He demanded an apology from Mr Maliki and said he would name the officials who tortured him in due course.
Hugh Sykes, BBC News, Baghdad
Many Iraqis regard Muntadar al-Zaidi as a national hero - others think he was unforgivably rude.
After leaving prison, Mr Zaidi went straight to al Baghdadiya, the TV station he was working for at the news conference where he threw the shoes.
Addressing his own news conference, he said he had been tortured in jail.
A spokesman for the ministry of human rights told us that if he was badly treated, it's likely that it happened while he was in custody before his trial, and not in the prison where he spent the past nine months, as it is a jail with a good reputation.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.