Emlyn was born in Pen-y-Ffordd, Mostyn, Flintshire, North Wales. He was born into a working-class family, but won a scholarship to Christ Church College, Oxford. In 1927, he joined a repertory company and began his stage career.

Night Must Fall (1935), which was later made into a film. His other great play was very different: The Corn is Green (1938). He often appeared in his own plays, >and was famous for his one-man-show, with which he toured the world, playing Charles Dickens in an evening of readings from Dickens' novels.

Emlyn also wrote two books: George, An Early Autobiography published in 1961 and Emlyn: An Early Autography, 1927-1935 published in 1974. Both his autobiographies were also highly successful.

By the time of his death in 1987, he had appeared in 41 films and teleplays, and written and/or co-written 20 screenplays.