The killing of Michael Diaz Milo, host of a daily radio show and a programme director of DXFM radio, further worsened the Philippines' standing as one of the most dangerous places for journalists.
The New York-based Committee to Protect Journalists (CPJ) ranks the Philippines as the third-worst in its "impunity index" of countries that fail to fight violence against the press.
Milo, 34, was riding his motorcycle in the coastal city of Tandag late Friday when men following him, also on a motorbike, shot him in the head, a police report said.
Police did not immediately give a motive for the killing but the radio station's operations chief King De La Rosa said that Milo had previously told him he had received death threats, although he did not say who sent them.
The victim had hosted a daily radio show on alternative medicine and local issues in Tandag, a small fishing and farming city on the troubled southern island of Mindanao.
Milo's killing comes a week after another broadcaster, Joas Dignos, was also shot dead by motorbike-riding assassins in Mindanao.
It is the latest in a series of unsolved murders of journalists in the Philippines.
The CPJ said at least 72 journalists had been murdered since 1992, not counting the cases of Dignos and Milo.
In one of the worst instances of such crimes, 32 journalists were among 58 people kidnapped and massacred, allegedly by a powerful political clan, in the southern province of Maguindanao in November 2009.
The trial of some of the accused in the massacre is ongoing but many of the accused remain at large.
President Benigno Aquino, elected in 2010 on a reformist platform, said his government would stop such murders but local media groups have accused his administration of not doing enough and of downplaying the killings.