Born and raised in San Francisco, Egan graduated from St. Ignatius College Preparatory and studied drama it while doing a BA at the University of San Francisco. His left school to join the army before returning to school for his master's degree in theater history from Stanford University. While teaching public speaking at Northwestern University, he appeared in thirty campus stage productions and was eventually spotted by a Warner Bros talent scout, Solly Bioano, who encouraged him to try Hollywood.
After beginning his career in 1949, he subsequently won a Golden Globe Award for his performances in the films: The Glory Brigade and The Kid from Left Field. He went on to appear in films, like The Damned Don't Cry, Underwater!, Seven Cities of Gold, The Golden Horde, The Revolt of Mamie Stover, Love Me Tender, A Summer Place, Esther and the King Blackbeard the Pirate, Wicked Woman, Seven Cities of Gold, Untamed, Violent Saturday, The 300 Spartans, and The House That Would Not Die.
Egan's television credits include the western drama Empire, The Streets of San Francisco, Matt Helm, The Quest, Police Story, and Capitol.
In 1974, he returned to the stage and for the next 8 years toured extensively in stage productions starting with No Hard Feelings, Time Out For Ginger, Hanky Panky, Broken Up, and I Ought To Be In Pictures.
He died 9 days before his 66th birthday.