- California Doubling: The castle of La Roche Goyon, better known as Fort la Latte, which is situated in Brittany, France, was used as Aella's Northumbrian castle.
- Dawson Casting:
- Kirk Douglas was one month older than Ernest Borgnine and played the latter's son. Borgnine sporting a beard and relatively long hair and Douglas being clean-shaven and short-haired helped sell the difference.
- Furthermore the character of Hasting (renamed "Einar" in the film) in the Edison Marshall novel, is stated to be two years older than Ogier (renamed "Eric" in the film).
- Eric is supposed to be around 20. Tony Curtis was 33 at the time.
- In the book, Morgana is stated to be fifteen, five years younger than Ogier/Eric when they first meet. Janet Leigh was 31.
- In the book, Egbert was thirty when Ogier was twenty. In the film he is played by the forty-one year old James Donald.
- Doing It for the Art: Kirk Douglas took no salary for the film in return for 60% of the profits, and was estimated to have earned $3 million from the film.
- Dyeing for Your Art: Kirk Douglas offered all the male members of the cast a prize for the best beard, to be grown before arriving on location. All turned up with huge beards, only to find Douglas clean-shaven.
- Produced by Cast Member: Kirk Douglas was the main producer of the film via his company, Bryna Productions.
- Production Posse: Kirk Douglas and Tony Curtis played in Spartacus two years later. Bryna Productions (Kirk's company) produced both The Vikings and Spartacus.
- Throw It In!: During the Viking Funeral scene, a single archer fires a flaming arrow, which hits the mast nearly dead center, followed by others. This was an accident, as one of the archers hired for the scene fired before he was supposed to. The director decided to keep it when he saw how good it looked.
- What Could Have Been: As the special feature on the DVD shows, before deciding on Eric for the renaming of Ogier the Dane, the character would have been called Oric. Similarly, Kirk Douglas' character would have been called Hastings instead of Einar, of course it is ambiguous if this is truly an Adaptational Name Change or merely a mispelling of the character's original name since even Edison Marshall once mispelled it as such.
Trivia / The Vikings