Defence Minister Mariusz Błaszczak signed the contract in Warsaw on Friday, Polish state news agency PAP reported.
He told reporters that the Polish army would receive "six squadrons" of Krab gun howitzers, 152 units in total, "to add to the six squadrons already ordered."
Błaszczak said Friday's contract represented "an important part of the drive to strengthen the Polish armed forces."
The defence minister said Poland was on track to create "Europe's strongest army" with 300,000 soldiers.
He added that the government was replacing Soviet-era weaponry with modern military equipment produced by domestic arms makers.
The Krab self-propelled gun howitzer is produced by Polish defence contractor PGZ.
The Krabs are being used by Ukraine's army in its war effort against the Russian invasion, according to reports.
The Krabs are fitted with a 155 mm howitzer that can strike targets up to 40 km away, and is also compatible with precision-guided munitions with a longer range of fire, the PAP news agency reported.
Friday is day 653 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Source: IAR, PAP