The second of six children to Anglican clergyman, Rev. Denis Murrell and Maude Williamson (née Watt) Deasey, Kathleen was educated at Geelong Church of England Girls' Grammar School. She obtained a BA (1931), MA (1933) and DipEd (1935) from the University of Melbourne, and a BA (1937) and MA (1946) from Newham College, Cambridge. She taught at Frensham, Mittagong, NSW and became lady superintendent at Methodist Ladies College (Melbourne).

In November 1941 Deasey was appointed assistant-controller, Southern Command and was promoted to Major on 28 January 1942. Initially she established the service's structure in Victoria and then supervised the enlistment and training of recruits. In May 1943 she was transferred to First Army Headquarters, Toowoomba, Queensland as assistant-controller and later to the Australian Army Chaplains' Department, Land Headquarters, Melbourne.

In 1944 the Chaplains' Department published, Readings and Prayers for Members of the Army Women's Services, a booklet that Deasey compiled. After the war she represented the Australian Women's Army Service at the Victory march in London (1946) and then returned to Australia and drafted a history of the Service.

After being discharged from the army Deasey worked with the Department of Immigration, spent time studying at the Sorbonne, Paris, followed by administering an agency sponsorship scheme for the World Council of Churches. From 1960 to 1961 she was a senior tutor in education at the University of Melbourne and then became Principal of St Ann's College, University of Adelaide, until 1966. Returning to Melbourne in 1967, she joined the staff of Larnook Domestic Arts Teachers' College, Armadale.

Kathleen Deasey, who never married, died on 6 September 1968 and was buried in Boroondara cemetery, Kew.

Sources used to compile this entry: MacIntyre, Eileen (1909-1968), 'Deasey, Maude Kathleen', in Australian Dictionary of Biography Online, Australian National University, 2006, http://www.adb.online.anu.edu.au/biogs/A130671b.htm.