Brian Castro was born at sea, between Macao and Hong Kong. His father was descended from Spanish, Portuguese and English merchants who settled in Shanghai at the turn of the century. He is also of Chinese descent through his mother, the daughter of a Chinese farmer and an English missionary. He has published in English, which was first taught him by his maternal grandmother but his first language was Cantonese Chinese, followed by English, Mecanese (a 'hybrid' Portuguese spoken in Macao) and French.
After arriving in Australia, he attended boarding school in Sydney and gained a Bachelor of Arts degree from the University of Sydney in 1971 and a Master of Arts degree from the University of Sydney in 1976. A secondary teacher until 1976, he spent one year teaching at the Lycée Technique Aulnay-sous-Bois, Paris. He returned to teaching for a period and then became a part-time milk deliverer and writer in the Blue Mountains. He won first prize in the 1973 Sydney University Short Story Competition and in the 1981 Nepean Review Short Story Competition. He has given public addresses, lectures and readings of his work at the Fellowship of Australian Writers (FAW), Katoomba, in 1982, the Multicultural Writers' Conference, Sydney, in 1984, Mitchell College and Orange Town Hall, in 1985, The Sydney Biennale, Art Gallery of NSW, in 1988, the Université de Paris, Nanterre, in 1988, The Université de Rouen in 1988 and at the Université de Toulous-Le Mirail, Toulouse, in 1988.
Also in 1988, Birds of Passage was translated into Chinese by Li Yao, President of the Writer's Association of Inner Mongolia, as was his other award winning novel, After China. In 1994 he was writer-in-residence at the University of Hong Kong and in the latter part of 1995 he was Writing Fellow at the Australian National University, the University of Canberra and University College, Australian Defence Force Academy.
In 2008, Castro was appointed to the position of Professor of Creative Writing, University of Adelaide.