Both sides, who agreed a truce over the weekend, sat facing each other in the Holmenkollen Park Hotel's "Nobel" room, named after the Nobel Peace Prize, with photographs of former winners including the Dalai Lama on the walls.
"This is a conflict that has been lasting for far too long," Norwegian Foreign Minister Boerge Brende told the meeting, saying there now seemed to be a "historic momentum" building to end the conflict, according to Reuters.
"I'm really crossing my fingers," for progress, he told the parties, each represented by six negotiators.
Talks brokered by Norway between the government and the Maoist-led rebels' National Democratic Front stalled in 2012 over the government's refusal to free communist leaders who had been in jail for decades.
Both sides declared a truce at the weekend to pave the way for the week-long talks in Oslo. Last week, Manila also freed 17 captured communist guerrilla leaders in the Philippines so they could attend the talks in Norway.
Philippine President Rodrigo Duterte had previously ended a unilateral truce with the communist New People's Army late last month as rebels did not respond to a deadline to reciprocate the government's truce.
The 3,000-strong New People's Army, the armed wing of the communist party, operates mainly in the eastern and southern regions of the country.