Families of personnel who died while serving in The Royal Welsh will attend the service, in front of the Bastion Wall memorial at the National Memorial Arboretum in Staffordshire.
They will visit the The Royal Welsh monument, built as a place of sanctuary and reflection.
Brig Philip Napier is due to address the families at midday.
Lt Col Chris Kilmister, regimental secretary of the Royal Welsh, said: "It is very fitting that we have gathered as the regimental family to pay our respects to all those who fell as the result of our fighting in Afghanistan."
The memorial replicates the design of the original Camp Bastion memorial wall at the UK's former Helmand Province base in Afghanistan, bearing the names of all 454 UK personnel who died in the conflict.
Welsh soldiers will commemorate the end of operations in Afghanistan during a ceremony on Saturday.