Watson had previously been Mayor of Toowong before the 1925 merger of the Brisbane councils. Archibald Watson was the Chairman of the Toowong Fire Brigade, which built a fire station in Jephson Street, Toowong, in 1919. Archibald Watson was (briefly) the last mayor of Town of Toowong prior to its amalgamation into Greater Brisbane in 1925.
The elections for an amalgamated Brisbane City Council were held on 21 February 1925.
He served as an alderman for Toowong between 1926 and his election loss in 1931. In April 1926, Hugh Russell the Deputy Mayor and Alderman for Toombul resigned to run for a seat in the State Assembly.
Watson was voted in as his replacement as Deputy Mayor. Upon William Jolly"s mid-term retirement in early 1931, Watson was then duly elected by a majority of Alderman Lord Mayor for a brief period between 24 February and 11 May 1931.
While on the Brisbane City Council, Archibald Watson served on the following committees:
Finance Committee 1925–1930
Tenders & Stores Committee 1925–1931
Parks & Recreation Committee 1925–1927 (Chairman)
Town Planning & Housing Committee 1925 (Chairman)
General Purposes Committee 1925
Transit Committee 1926–1931 (Chairman)
Licensing Committee 1926–1937
Markets & Miscellaneous Committee 1926–1927
Resumptions Committee 1926–1927
Electric Light & Powerhouse Committee 1928–1931 (Chairman)
Water Supply & Sewerage Committee 1929, 1931
After his landslide 1931 election defeat, Watson was never elected to Brisbane City Council again.
After the formation of the anti-Labor Citizens Municipal Organization, Watson unsuccessfully sought to be nominated as the CMO Lord Mayoral candidate, with the incumbent John William Greene being selected. He died, in 1941, aged 66 years after a long illness.