Barry Fitzgerald, who plays the character of Cocky, and Arthur Shields, who played Donkeyman, were brothers in real life. They also appeared together in director John Ford's L'homme tranquille (1952).
John Wayne once told biographer Maurice Zolotow: "Usually it would be Mr. Ford who helped the cinematographer get his compositions for maximum effect . . . but in this case it was Gregg Toland who helped Mr. Ford. 'Long Voyage' is about as beautifully photographed a movie as there ever has been."
John Wayne was asked by director John Ford to play the part of Ole Olson, who was Swedish. Wayne wasn't sure he could pull off the Swedish accent and was worried that the audience would laugh. Ford persuaded him to take the role.
The name of Arthur Shields' character, "Donkeyman", is a nickname for the job he performed, the sole caretaker of the ship's single-piston "Donkey" engine.
Eugene O'Neill's favorite film. John Ford gave him a print of it, which he wore out from repeated playing.