Three Kuwaiti citizens were arrested and have confessed to joining a "terror" group, a statement said.
Security forces seized "19 tonnes of ammunition" as well as 144 kilos (316 pounds) of TNT, as well as rocket propelled grenades, hand grenades, firearms and detonators, the ministry said.
It said the explosives were found in a farm in Abdali, near the border with Iraq, and in two houses in undisclosed locations.
At the end of July, Kuwait said it had broken up a five-member cell of alleged members of the Islamic State group.
Last month, Kuwait said it had broken up a five-member cell of alleged IS militants.