Greg Cullen was born into the Irish community in London. He was educated at St. Mary's University College, Strawberry Hill, studying Drama, Art and Education. In 1983 he became writer-in-residence with Theatr Powys for whom he wrote a wide variety of plays. In 1987 he founded Mid Powys Youth Theatre, and in 1992 was appointed writer-in-residence at the Welsh College of Music and Drama. In 1997, Birdbrain, a short film, won the BBC/Wales Film Council 'PICS' competition and a BAFTA award.