Ingrid Bergman was the first choice to play Terry McKay.
Deborah Kerr and Cary Grant improvised many of their scenes throughout filming, and a number of lines that made it to the final cut of the film came from the actors' improvisation.
Deborah Kerr plays Terry McKay, previously played by Irene Dunne in Love Affair, of which this film is a remake - both were directed by Leo McCarey. The year before this film was made, Kerr played Anna Leonowens in The King and I, also a role that had previously been played by Irene Dunne in the black-and-white classic Anna and the King of Siam. "The King and I" is a musical based on the same book.
Deborah Kerr's singing was dubbed by Marni Nixon, who also dubbed her in The King and I the previous year.
A Bollywood film with the title Mann starring Aamir Khan and Manisha Koirala was inspired by this movie.
After the confrontation with the photographer on the ship's deck, Deborah Kerr turns to Cary Grant and says, "So, I go my way traces a straight path by her hand and you go yours traces a twisty path with the waive of her hand." The same exchange takes place between Irene Dunne and Cary Grant in The Awful Truth, where she says: "As we go down the life's highway, you go in your way traces a twisty path with the waive of her hand and I go in my way traces a straight path."
In the "50th anniversary" DVD release, one of the bonus features is a Movietone News piece about the shipboard premiere of the movie aboard the S.S. Constitution, identified in the newsreel as the location for filming.
Nickie and Terry make their conditional promise to meet in six months at exactly the halfway point of the film (59-1/2 minutes into the 119-minute movie).
References to this movie in Nora Ephron's Sleepless in Seattle, revitalized interest in the film, and led to 2 million additional sales of the 1957 classic on VHS.
Was voted the #5 greatest romance of all time by the American Film Institute. This is the highest voted film in which the two lovers end up together in the end.