For years, John Saxon said he had been bothered by something about Sandra Dee during filming that he just couldn't put his finger on. Decades later, he figured out what it was: Dee's mother had lied about her age to get her more adult roles. She was only 16 years old at the time of filming.
The film was shot in Paris because Rex Harrison was having tax problems and could not go to the U.S. or the U.K.
This was the only film that Rex Harrison and Kay Kendall made together during their marriage. Kendall died from leukemia the following year at the age of 32.
Because there was a musicians' strike at the time this movie went into post-production, only recycled source music is heard in the ball sequences, while the main title theme was lifted verbatim from the soundtrack of another Vincente Minnelli comedy, Designing Woman (1957).
Loosely remade as What a Girl Wants (2003), which carries the end credit "based on the play 'The Reluctant Debutante' by William Douglas Home"