The U.S. military acknowledged on Saturday killing 23 civilians and wounding 12 others earlier this year after mistaking them for a convoy of Taliban insurgents.
The U.S. report into the incident, which happened in Uruzgan, said the crew of a remote-controlled drone aircraft had "provided inaccurate reporting" ahead of the incident and local command posts "failed to properly analyze the situation".
"Information that the convoy was anything other than an attacking force was ignored or downplayed by UAV (unmanned aerial vehicle) personal," it said.
The Taliban are responsible for the majority of civilian conflict deaths in the country, but the issue is a sensitive one for U.S.-led foreign troops, who are frequently accused of using indiscriminate firepower - even in civilian areas - to fight the insurgency.
The U.S. counterinsurgency strategy emphasizes seizing population centers and avoiding combat in built-up areas whenever possible to avert civilian deaths.
Taliban fighters, however, frequently plant bombs, launch suicide raids and attack government and Western targets in civilian areas.
The U.S. report into the Uruzgan incident cited operational shortcomings in training, communication and decision-making and offered recommendations to prevent future incidents.
The Afghan government said at the time that 27 civilians had died and 12 others were injured - including several women and children.
"Our most important mission here is to protect the Afghan people," the commander of foreign troops, General Stanley McChrystal, said in a statement.
"Inadvertently killing or injuring civilians is heartbreaking and undermines their trust and confidence in our mission. We will do all we can to regain that trust."
Four officers - including senior leaders at battalion and brigade level, had been officially reprimanded, the report said, while two junior officers were formally admonished.
The Taliban have steadily widened the revolt they have waged since being ousted in 2001, and now face off against over 140,000 mostly U.S. or NATO troops - mostly in the south and east of the country.
That number is expected to increase in coming weeks through a surge ordered by U.S. President Barack Obama as they prepare for a major offensive against Taliban elements in Kandahar, where the insurgents draw much of their support.