A by-election for the seat of Guildford-Midland in the Legislative Assembly of Western Australia was held on 13 March 1948.
It was triggered by the death of the sitting member, William Johnson of the Labor Party, on 26 January 1948.
The Labor Party retained the seat, with John Brady recording 53.7 percent of the two-party-preferred vote.
William Johnson had held Guildford-Midland for the Labor Party since its creation at the 1930 state election.
Johnson died at St John of God Subiaco Hospital on 26 January 1948.