They died from injuries sustained whilst on patrol in the Nahr-e Saraj district of Helmand province.
Spokesman for Task Force Helmand, Major Laurence Roche, said:
I am extremely sorry to announce the deaths of a Royal Marine from 40 Commando and a soldier from 3 Medical Regiment serving with Task Force Helmand.
This is dreadful news for all of us serving in Afghanistan. Our sincere condolences go to their families, friends and colleagues at this time of grief.
Next of kin have been informed and have asked for a period of grace before further details are released.