During the Cold War the Korean War broke out when communist forces from the north invaded the south on 25 June 1950. Under the auspices of the United Nations 15 nations, headed by US forces, defended the south.
The New Zealand Government formed an emergency force to contribute to this UN response. Called K-Force or Kayforce, it comprised artillery and support services supplemented by ships of the Royal New Zealand Navy. An armistice in July 1953 saw active combat cease, and New Zealand maintained a reduced presence in Korea until July 1957. The Korean commitment from 1950 to 1957 cost the lives of 45 New Zealanders, 33 during the war itself. New Zealand still participates in the UN mission to monitor the armistice (North Korea and South Korea are still technically at war).
Four New Zealand servicemen named Matheson (and none named Mathieson) are listed in the online New Zealand Korea service roll as having taken part in Kayforce.
| Name Service number | Force | Rank | Details |
| Graeme Thomas Neill Matheson 13637 | Navy | Leading Mechanic (Engineering) | Born Oamaru 1933. Was a Post & Telegraph Mechanic before he enlisted in the RNZN in 1951 as a Stoker. Served on board the Bellona from 1952 to 1953 and Lachlan 1954 to 1955. Drafted to the Pukaki in February 1955 and served on Korean operations from April 1955 to April 1956. Remained in the Navy until 1959. Died at Rangiora in 2026 aged 92. |
| John William Leonard Matheson 206019 | Army | Gunner | Born Winton, Southland, 1925. Also served in Jayforce in 1948. Enlisted again in 1950 and left for Korea where he served with the 16 (NZ) Field Regiment, returning in 1952. Died at Lyttelton in 1969 aged 43 years. |
| Kenneth Graham Matheson 203753 | Army | Trooper | Born Whangarei 1925. Also served in WW2 (RNZAF) and Jayforce. Was working as a millhand in Rotorua when he enlisted in Kayforce in 1950. Served overseas 1950–1952, first at the NZ Base Ordnance Section and then the 16th Field Regiment. Died at Rotorua in 1975 aged 50 years. |
| Trevor Dickinson Matheson 208869 | Army | Driver | Born Dunedin 1927. Worked as a driver. Served in Korea 1953–1954, mostly in an army transport unit. Died in 2007 aged 74. Buried at Greenpark RSA Cemetery, Dunedin. |
Kenneth Graham Matheson