Patrick O'Brien was a draftsman in a naval architecture firm and earned a degree in biology from the University of Virginia before attending art school. An illustrator and painter since 1985, he specialized in historic and prehistoric subjects, working with such clients as National Geographic, The Discovery Channel, The Smithsonian, and the U.S. Naval Institute. His artwork has appeared in magazines and newspapers, on posters and greeting cards, and even on billboards.

In 2003 he entered the marine art field. His first entry to the annual Mystic International Marine Art Exhibition won an Award of Excellence. At Mystic in 2007 his entry was used as the cover of the catalog for the show, and in 2010 his entry won the Museum Purchase Award, which means that Mystic Seaport Museum bought the painting for its permanent collection.