Before "going Hollywood", he was a successful playwright and producer on Broadway. In 1912 he produced the hit play "Within the Law," which netted approximately $1 million (appromximately $19 million in 2003 dollars) in those pre-income tax days. He was president of Selwyn & Company, Inc., a theatrical production company he owned with his younger brother Archibald Selwyn and Crosby Gaige, from 1914 to 1924.
Edgar and Ruth Selwyn divorced before his death in 1944. They had one son, Russell (nicknamed "Rusty"), who was born during Ruth's previous marriage to a man surnamed Synder, and who was adopted by Edgar during their marriage.
He became a movie producer with his brother Archibald Selwyn in 1912, eventually merging their All-Star Feature Films Corp. with Samuel Goldfish's (soon to change his name to Samuel Goldwyn) studio to create Goldwyn Pictures Corp. in 1916. He was hired by Metro-Goldwyn-Mayer in 1929 as a writer and director, eventually becoming a producer and serving as an editorial assistant to Louis B. Mayer while operating his own production unit.
He was an actor-playwright in stock companies and on Broadway after the turn of the last century. His first play was the one-act "A Night in Havana" for a stock company. He adapted Gilbert Parker 's novel "Pierre and His People" as "Pierre of the Plains" and acted in it on Broadway in 1911. Also in that year he had his biggest success with his play "The Arab," in which he also starred.