Born at Perranzabuloe in Cornwall to carpenter William Allen and Salome Williams, he came to Parramatta in 1879 and from 1884 worked as an articled clerk to a Sydney architect, subsequently becoming a civil engineer.
After moving to Western Australia in 1894, he married Jean Symington Buntine on 25 September 1900.
In 1903 Allen was elected to East Fremantle Municipality, on which he would continue to serve (with a one-year break) until his death.
In 1914 he was elected to the Western Australian Legislative Council as a Liberal member.
He was re-elected mayor of East Fremantle in 1931 but died suddenly in 1933; his body was found in the Swan River, but the coroner ruled no suspicious circumstances.