The soldier, whose identity was not released, was injured in the military camp at Karbala, southwest of Baghdad, and was taken to the town's hospital where he died, ministry spokesman Adam Stasinski told AFP.
He was the second Polish soldier to die in Iraq.
On November 6, a 44-year-old Polish officer was shot and killed during an attack on a military convoy about 40 kilometers (25 miles) northeast of Karbala.
The accident occurred the same day as Polish President Aleksander Kwasniewski made a surprise a morale-boosting pre-Christmas visit to the main Polish base at the central town of Hilla.
Kwazniewski was accompanied by Defence Minister Jerzy Szmajdzinski and his security chief, Marek Siwiec.
Polish troops fought alongside those of the United States and Britain in the war that toppled Iraqi leader Saddam Hussein eight months ago.
It now heads a multinational force patrolling a large swathe of central and southern Iraq. It has 2,350 soldiers in the country.