The unidentified soldier "died as a result of wounds sustained during operations" yesterday in Logar province, south of Kabul, US Forces said.
The incident comes days after another US soldier died following a helicopter crash in the same province that also wounded six US crew members.
US soldiers have been mainly in a non-fighting role in Afghanistan since the end of 2014 when NATO combat troops withdrew from the country.
That has made US battlefield deaths relatively rare.