"Yes, we have decided to buy the tanks," Mahathir told journalists at the end of a four-day visit to Poland devoted to arms purchases.
The exact number of tanks to be purchased remains open, and Malaysia wants to pay in commodities rather than cash, he added.
Polish Defense Minister Jerzy Szmajdzinski said Thursday that Warsaw had offered 64 tanks and armored vehicles for RM950 million, and the sum could reach up to RM1.1 billion with supplementary equipment and services.
Mahathir did not indicate when the deal was likely to be wrapped up, but Polish officials have said they expect all the details to be worked out by the end of this year.
In addition to continuing talks on what commodities Poland will accept as payment for the tanks, Malaysia is seeking offset contracts and technology transfers.
"There will be various offset arrangements in order to benefit both sides... There will be other discussions on technology transfer," he told journalists.
Mahathir met with his Polish counterpart Leszek Miller on Thursday.
Mahathir, accompanied by Malaysian Defense Minister Najib Tun Razak, attended a weapons demonstration by a Polish armored unit near Warsaw and a revue of a Polish naval unit on the Baltic Sea coast.