Cocks trained as a teacher and took up a position with the South Australian Education Department. She taught at several schools and became sub-matron of the Industrial School at Edwardstown, Adelaide. In 1906 she took up a post in the Child Welfare Department of the State Children's Council and three years later became the state's first probation officer working to reduce the number of juvenile offenders who might be placed in institutions.

In 1915 Cocks was appointed the first woman police officer in South Australia, and possibly the British Empire, with the same rate of pay and same powers as the policemen. The responsibilities of Cocks and her assistant Annie Ross included protecting young women and children from violence or from being drawn into crime or prostitution, patrolling the nighttime streets and dance halls for those underage and handling female offenders. Cocks also at times took homeless girls into her home.

Cocks retired from the police force in 1935 to nurse her ailing mother. She advocated for the Methodist Women's Home Mission Association to open a refuge for homeless girls and a house was purchased for this purpose. Also in 1935, Cocks was appointed the Superintendent of the Methodist Women's Welfare Department. In 1936 the Methodist Church established a shelter for unmarried women with newborn infants and other needy youngsters. Cocks superintended this home from 1937 and later it was re-named in her honour.

1915: Appointed South Australia's first woman police officer - possibly the first female police officer in the British Empire - and was founding principal of the women's branch of the South Australian Police

1935: Awarded Order of the British Empire (MBE)

1935-51: Superintendent of the Methodist Women's Welfare Department

Kate Cocks became well-known for her nightly patrols of the parklands around Adelaide on the lookout for young people behaving amorously. Her catchphrase became 'three feet apart, three feet apart!'

Kwan, Elizabeth. Living in South Australia : a social history, volume II, Netley, S. Aust. : South Australian Government Printer, 1987

O'Neill, Dorothy. Kate : Fanny Kate Boadicea Cocks, M.B.E. 1875-1954 : the story of a woman with purpose, Henley Beach, S. Aust. : Seaview Press, 2005

Australian Women's Register: Search for Kate Cocks

South Australia Police Historical Society: See: Women Police