Mariusz Błaszczak signed the deal at a high-profile ceremony in Morąg, northern Poland, on Friday, state news agency PAP reported.
Under the agreement, Poland will buy 180 K2 tanks from South Korea's Hyundai Rotem company and 212 K9 self-propelled howitzers from the Hanwha Defense company, officials told reporters.
"The contract with Hyundai Rotem provides for the delivery of 180 K2 tanks in 2022-2025," the Polish defence ministry said in a tweet.
Meanwhile, "the contract with Hanwha Defense provides for the acquisition of 212 K9 family self-propelled howitzers in 2022-2026," it added.
"The first tanks and howitzers will be delivered to Poland later this year," the Polish defence ministry also said.
"What we have achieved with our South Korean partner is impressive," Błaszczak said during the ceremony, as quoted by his defence ministry.
"We have achieved a lot in a short time," he added. "In this way, we strengthen Poland's defence."
The Polish defence ministry said that the military equipment ordered from South Korea would help strengthen Poland's "deterrence and defence potential."
Ultimately, some of this equipment will be produced "with a wide participation of the Polish armaments industry," it announced.
Błaszczak last month approved a framework agreement for the purchase of fighter jets, tanks and howitzers from South Korea for the Polish armed forces, according to reports at the time.
Błaszczak, who is also a deputy prime minister, said in late July that Poland aimed to build the strongest army among NATO members in Europe.
In June, he told reporters after talks with officials in Seoul that Poland would purchase modern weapons from South Korea to boost its security after Russia's invasion of neighbouring Ukraine.
Saturday is day 185 of Russia's war in Ukraine.
Source: IAR, PAP