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. The election was notable for the performance of the Communist Party candidate, Alexander Jolly, who polled 19.3 percent on first preferences (one of the party's highest totals in Western Australia).