Sultan Abdullah of Pahang state took his oath in a ceremony held at the national palace in Kuala Lumpur, with other rulers of Malaysia taking part in the event.
The nationally televised ceremony was attended by Prime Minister Mahathir Mohamad, cabinet ministers and hundreds of guests.
Abdullah was chosen the new king by nine Malay royals for a five-year-term last week after the previous monarch abdicated his post following his reported marriage to a Russian beauty queen.
Sultan Abdullah, 59, is an avid sportsman and a member of the FIFA council.
Malaysia is a constitutional monarchy with a federal representative character. The king is the ceremonial head while the prime minister oversees daily governance.
On Jan. 6, former Sultan Muhammad V rendered a shock resignation, a first in Malaysian history.