A by-election was held for the New South Wales Legislative Assembly seat of Vaucluse on Saturday, 24 August 1957. It was triggered by the resignation of the former Leader of the New South Wales Liberal Party, Lt.Col. Murray Robson, who retired from parliament. The seat was subsequently won by Brigadier Geoffrey Cox of the Liberal Party of Australia. Vaucluse being a blue-ribbon Liberal seat, the Labor Party chose not to field a candidate. The Liberals witnessed a drop in their primary vote due to several Independent Liberal candidates splitting the strong conservative vote.