All are suspected of links to the so-called Islamic State (IS) militant group said the national police chief.
The 15, including one police officer, were arrested over three days in the capital, Kuala Lumpur, and six other states, said Khalid Abu Bakar.
One hundred and seventy-seven suspected militants have been detained in Malaysia in the past three years.
The authorities said the suspects were trying to obtain chemicals to make bombs and were planning to launch attacks. They were aged between 22 to 49 and included four women who were planning to travel to Syria to join IS, they said.
The police chief said the group also arranged for two foreign terror suspects to sneak out of Malaysia, and had channelled money to militants in the southern Philippines.
Malaysia is on a particularly high terror alert since the capital of neighbouring Jakarta was attacked by militants in January.
On 15 January, Malaysian police said they had arrested a man they claimed was hours from carrying out a suicide attack in Kuala Lumpur.
Malaysian authorities say 15 people suspected of planning attacks on the country have been arrested.