D. K. Broster was born on 2 September 1877, to Thomas Mawdsley Broster and Emilie Kathleen Gething, at Devon Lodge (now Monksferry House) in Grassendale Park, Garston, Liverpool, on the banks of the Mersey. "And to this she probably owed her life-long interest in the sea." When she was 16, the family moved to Cheltenham, where she attended Cheltenham Ladies' College. From 1896 to 1898 she read history at St Hilda's College, Oxford, where she was one of the first students, although at this date women were not awarded degrees.