Gilberte is a sixteen year old girl raised by her aunt and grandmother to be a demimondaine. But she's not ready for that yet, and spends her days in lessons and in teasing Mamita's old friend, the rich playboy Gaston LaChaille, and following his affairs from afar. But when Gaston throws off his latest mistress, it looks as if Gigi just might be ready to begin her destined career.
Jimmy and Sheila Broadbent (Rex Harrison and Kay Kendall), welcome to London Jimmy's 17-year-old daughter, Jane (Sandra Dee). Jane is from Jimmy's first marriage to an American and has come to visit her father and the step-mother she has never met. While visiting Sheila has the idea of making Jane a debutante, an idea Jane resists. Difficulties range from Jane's apathy to being placed on the marriage block, the determined efforts of Sheila's cousin, Mabel Claremont, (Angela Lansbury) to win wealthy David Fenner (Peter Myers) for her debutante daughter Clarissa (Diane Clare), and Jane's attraction to David Parkson (John Saxon), an American drummer who plays in the orchestra at the coming-out balls.