al-Shaalan was born in Diwaniyya, southern Iraq, into a leading family of the Ghazal tribe. He is a is a Shia Arab. He graduated from Baghdad University with a degree in Economics and was an inspector general of the Iraqi Real Estate Bank from 1983 until he left Iraq in 1985. He managed a real estate firm in London until the invasion of Iraq in 2002, after which he returned to Iraq. An Iranian news agency reported documents showing that al-Shaalan had been a member of Saddam Hussein's secret police, the Mokhaberat.
A member of Ahmad Chalabi's Iraqi National Congress, he was appointed Governor of Al-Qādisiyyah Governorate in 2003 and then as Iraq's Defence Minister from June 2004 until May 2005 under the Iraqi Interim Government of Ayad Allawi. He appointed Ziyad Cattan, as the Defence Ministry's procurement chief, who has since fallen under suspicion of involvement in the greatest theft in history- embezzling $1bn intended for weapons purchase. al-Shaalan had received an exemption from the cabinet for having his ministry's expenditures overseen by the cabinet's audit committee. al-Shaalan claimed that the Coalition Provisional Authority's interim administrator of Iraq, Paul Bremer, had signed off the appointment of Cattan, but Bremer claims he had never heard of Cattan.
In August 2004 he said Iran was Iraq's "prime enemy"
He stood with Ghazi al-Yawar's Iraqi List in the Iraqi legislative election of January 2005. Shortly before the election he threatened to arrest Ahmed Chalabi for "tarnishing the reputation of the Defense Ministry and the Defense Minister." His bodyguards also clashed with Iraqi security forces in Diwaniya during campaigning for the January election
Ali Allawi, the Finance Minister in the Iraqi Transitional Government, accused al-Shaalan of embezzlement in 2005, and Iraq's anti-corruption watchdog, the Commission for Public Integrity, sought to bar him from running in the following parliamentary elections. He formed the "Parliament of Patriotic Forces" list for the Iraqi legislative election of December 2005, but failed to win any seats.
The Independent says both al-Shaalan and Cattan left Iraq in 2005 for Jordan.
In May 2007 al-Shaalan was convicted in absentia of embezzlement and sentenced to 7 years imprisonment.