Police said Percival Mabasa, 63, was driving his vehicle in suburban Las Pinas City on Monday night when two men on a motorcycle approached and shot him twice in the head.
Work to identify and locate the attackers, who escaped, was underway, police officials said.
They said investigators were trying to determine the motive for the attack.
Mabasa, who used the broadcast name Percy Lapid, was critical of former president Rodrigo Duterte — who oversaw a deadly crackdown on illegal drugs — and current leader Ferdinand Marcos Jr, the son of a dictator who was ousted in a 1986 pro-democracy uprising.
Media watchdogs condemned Mabasa’s killing, saying the attack underscored how deadly the Philippines remained for journalists.
Amnesty International said the attack bore “all the hallmarks of an extrajudicial execution and an attempt to silence voices critical of the government”.
The victim’s family condemned the “brutal and brazen killing” and demanded that the perpetrators to be brought to justice.
Mabasa is the second journalist killed during Mr Marcos Jr’s time in office, which began in June.
Radio broadcaster Rey Blanco was stabbed to death during an altercation last month in central Negros Oriental province. The suspect immediately surrendered to police.
Nearly 200 journalists have been killed in the Philippines since 1986, when Ferdinand Marcos Sr was overthrown, according to the journalists’ union.