The new leader was sworn in on Tuesday.
The Western-educated Hun Manet, 45, had the backing of the majority of the National Assembly in proceedings screened live on television.
His father, Hun Sen, a former Khmer Rouge guerrilla and self-style strongman, has pledged to remain in politics in other roles for at least a decade.
A graduate of the West Point military academy in the United States, Hun Manet rose fast through the ranks of Cambodia's armed forces and has served as head of counter-terrorism, deputy chief of his father's bodyguard unit, army chief and deputy military commander.
He is also highly educated, with a masters degree from New York University and a doctorate from Britain's Bristol University - both in economics - in stark contrast to his father, who had no formal education.
Hun Manet's first months in office will be watched by major powers for signs of whether he favours a more liberal approach and improvements in Cambodia's strained ties with the West, or plans to keep the authoritarian status quo of his father and remain in China's sphere of influence.
Little is known about Hun Manet's vision for Cambodia, a country of 16 million people, few of whom have lived under a leader other than his father.Â
