Seymour Barry, brother of comic artist Dan Barry, studied at the New York School of Art and Design. When he graduated, he went to the Art Students League, while working as an assistant to his brother. In the late forties and early fifties, Sy Barry did freelance work, mainly as an inker, for comic book companies such as Gleason, Marvel and especially National, where he worked on the features 'Jonny Peril', 'Rex' and 'Phantom Stranger'.
In the late fifties, he assisted his brother again with the inking of 'Flash Gordon'. This job put him in contact with the King Features editors, who asked him to take over 'The Phantom' after Wilson McCoy's death in 1961. After drawing the adventures of the Ghost-Who-Walks for over 30 years, he retired in 1995.