McCutcheon is best remembered for two kinds of novels. First, he pioneered the "Graustarkian" romance with Graustark (1901), a tale set in a fictional Eastern European kingdom full of romance and adventure. Its success spawned several sequels, including Beverly of Graustark (1904), Truxton King (1909), and The Prince of Graustark (1914). Second, he wrote the comic classic Brewster's Millions (1902), about a young man who must spend a million dollars within a year to inherit a far larger fortune. The book proved enduringly popular and was adapted for stage and screen many times, most notably the 1985 film starring Richard Pryor.
His other notable works include The Day of the Dog (1904), Jane Cable (1906), The Hollow of Her Hand (1910), and Anderson Crow, Detective (1920).