Seven U.S. service members and three U.S. civilians died in the single-helicopter crash, which injured 14 U.S. service members, one U.S. civilian and 11 Afghans.
The helicopter was involved in an anti-drug operation in Badghis province in northwestern Afghanistan.
The dead service members were part of U.S. Special Operations forces, a U.S. defense official said.
In a separate incident, four U.S. service members were killed and two injured when two helicopters collided and crashed in southern Afghanistan.
The “separate tragedies today underscore the risks our forces and our partners face every day,” said a spokesman for the International Joint Security Forces Operations.
Neither incident resulted from hostile fire, according to the military.
This has been the deadliest year for international and U.S. troops since the 2001 invasion of Afghanistan. August was the deadliest month yet for U.S. soldiers in the country, with 51 troops killed.
Forty-three U.S. troops have died so far this month.
White House Weighs Afghan Strategy
The deaths come as President Obama weighs whether to send tens of thousands more troops to the country and the Afghan government struggles to organize a runoff election Nov. 7 between President Hamid Karzai and top challenger Abdullah Abdullah after allegations of widespread fraud tainted the August vote.