Under the plan, a helicopter-equipped destroyer and two P-3C patrol planes will be dispatched for information-gathering aimed at ensuring safe passage for Japanese vessels through the region.
If there are any emergencies, a special order would be issued by the Japanese defense minister to allow the forces to use weapons to protect ships in danger.
Friction between Iran and the United States has increased since last year, when U.S. President Donald Trump pulled the United States out of a 2015 international nuclear deal with Iran and re-imposed sanctions on it, crippling its economy.
In May and June, there were several attacks on international merchant vessels, including the Japanese-owned tanker Kokuka Courageous, in the region, which the United States blamed on Iran. Tehran denies the accusations.
Japan, a U.S. ally that has maintained friendly ties with Iran, has opted to launch its own operation rather than join a U.S.-led mission to protect shipping in the region.
Last week, Prime Minister Shinzo Abe briefed visiting Iranian President Hassan Rouhani on Tokyo's plan to send naval forces to the Gulf.
The planned operation is set to cover high seas in the Gulf of Oman, the northern Arabian Sea and the Gulf of Aden, but not the Strait of Hormuz, the cabinet-approved document showed.
The Japanese government aims to start the operation of the patrol planes next month, while the destroyer will likely begin activities in the region in February, a defense ministry official said.A European operation to ensure safe shipping in the Gulf will also get underway next month, when a French warship starts patrolling there.