It is situated on the eastern bank of the Helmand River on 31°07′00″N 64°12′00″E / 31.1167°N 64.2000°E / 31.1167; 64.2000 at 714 m altitude and 63 km southwest of Lashkargah.

[citation needed] Garmsir has a hot desert climate (Köppen BWh), characterised by little precipitation and high variation between summer and winter temperatures.

Garmsir was the scene of heavy fighting during April–September 2008 when U.S. Marines from the 24th MEU arrived to reinforce British and Afghan forces.

In July 2009, Marines taking part in Operation Khanjar met little or no resistance initially.

By July 5, elements of the 2nd Battalion, 8th Marines were engaged in heavy fighting with Taliban forces.