Baroness Emmuska Orczy was born in Tarnaörs, Hungary, as the only daughter of Baron Felix Orczy, a noted composer and conductor, and his wife Emma. Her father was a friend of such composers as Wagner, Liszt, and Gounod. Orczy moved with her parents from Budapest to Brussels and then to London, learning to speak English at the age of fifteen. She was educated in convent schools in Brussels and Paris. In London she studied at the West London School of Art. Orczy married in 1894 Montague Barstow, whom she had met while studying at the Heatherby School of Art. Together they started to produce book and magazine illustrations and published an edition of Hungarian folktales.

Orczy's first detective stories appeared in magazines. As a writer she became famous in 1903 with the stage version of the Scarlet Pimpernel.