He attended Erasmus High and Brooklyn College, and served a brief stint in the United States Army.
O'Brien worked as a press agent, publicizing clients including comedians Woody Allen,[5] Bill Cosby, Joan Rivers, Victor Borge, Dick Cavett and Rodney Dangerfield.
O'Brien's research led to the publication of Collecting Toys, released in 1985 by Books Americana.
He later sold the copyright to Krause and the series was continued under his name with Karen O'Brien (no relation) as editor.
[13] O'Brien also published a number of articles with information about toy-soldier firms, including Barclay, which were later compiled in a series of books available through Ramble House.