The 853 soldiers and officers of the 31st Battalion graduated on Sunday morning in a ceremony in the capital Kabul.
"You young people must encourage others to follow you into the Afghan National Army," General Abd Allah, a senior Defence Ministry official who goes by one name, told the soldiers.
"You are entrusted with the Afghan nation and must go like men to every corner of the country."
The Afghan National Army now numbers more than 20,000, but officials said they had no precise figure.
A new multi-ethnic army is a key provision of international accords on rebuilding a strong Afghan government.
The accords were signed in December 2001 after US forces invaded Afghanistan.
The Afghan force is supposed to replace armed factions tarnished by their role in Afghanistan's civil wars.
More than 42,000 people have been disarmed under a UN programme.
The force is also expected to take a growing role in the battle against fighters in the country's south and east, often in conjunction with the 17,000-strong US force focused on remote provinces along the Pakistan border.
Recruitment to the new army was initially dogged by desertions and poor pay.
But conditions have improved, and US officials say six battalions will be in training simultaneously starting next month, up from two at the start of last year.
The force is supposed to reach its full strength of 70,000 by the end of 2006.