"I accept the verdict of the people," the leader, who looked shattered after his coalition's defeat, said. But he added that because no single party got a majority in parliament, it was up to the king to decide who will become prime minister.
Mahathir's opposition won 121 seats, if a small ally from Sabah state is included. There are 222 seats in parliament and a majority is needed to form a government.
The veteran ex-leader, who led the country with an iron first for over two decades, stormed to a shock victory at the hard-fought election early Thursday, beating Najib's Barisan Nasional (BN) coalition that has been in charge for over six decades.