Deakin was born at 90 George Street, Fitzroy, Melbourne, and began his education at the age of four in a boarding school that was initially located at Kyneton, but later moved to the Melbourne suburb of South Yarra. In 1864 he became a day pupil at Melbourne Church of England Grammar School, but did not study seriously until his later school years, when he came under the influence of J. H. Thompson and the school's headmaster, John Edward Bromby, whose oratorical style Deakin admired and later partly adopted. In 1871 he graduated with good passes in history, algebra and Euclid and basic passes in English and Latin. He began evening classes in law at the University of Melbourne, while working as a schoolteacher and private tutor. He also spoke frequently at the University Debating Club founded by Charles Henry Pearson in 1874, read widely, dabbled in writing and became a lifelong spiritualist, holding the office of President of the Victorian Spiritualists' Union.