Grace Kelly became a real princess when she married Prince Rainier of Monaco the same year that this film was released.
The only film in which Grace Kelly plays a princess (she later became one in real life). In this film, she is courted by Prince Albert of a small European country. Prince Albert of Monaco is Grace Kelly's son.
This was the second time in two years that Jessie Royce Landis played Grace Kelly's mother. The first was in To Catch a Thief. These were the only two films in which both actresses appeared together.
While filming The Swan in Hollywood, Alec Guinness he met James Dean, just days before the young actor's death. Sir Alec later recalled predicting that Dean would die in a car crash: when Dean showed Guinness his newly-bought Porsche, Guinness advised him to "Get rid of that car, or you'll be dead in a week!" Guinness unfortunately proved right.