As prostitutes are arrested in New York, a flashback begins to the life of one of them, a Dutch secretary Xaviera Hollander (Redgrave) who moved to New York in hopes of marrying her fiancé Carl (Nicholas Pryor), whom she met whilst visiting her sister in South Africa.
Observing how Carl does not help her take her bags off the airplane and his increasingly long morning routine and primping, Xaviera grows concerned he is not the man she thought he was. Her suspicions are confirmed when his mother insults her over dinner. Xaviera offers him a choice of her or his mother and he picks his mother.
Xaviera finds work at the Dutch Embassy as a translator and secretary. She is asked on a date by Frenchman Yves (Jean-Pierre Aumont) and quickly falls in love with him and his extravagant lifestyle, as Yves has made a small fortune as a consultant for large corporations and even small countries.
Yves announces that he must leave as he has been summoned by the king of a Middle Eastern country. Xaviera breaks down crying. He hands her a large envelope containing cash. Although it makes her feel like a prostitute, she realizes quickly that this may be her calling in life because she loves sex and money. She starts meeting up with Yves' friends.
Xaviera prospers as a prostitute until she is shaken down by a corrupt cop (Richard Lynch) who takes her money and tries to rape her. Instead of paying him off, she goes to work at a local bordello with a madam who offers her a 50/50 split. Xaviera decides that she can do better on her own, so leaves to open her own bordello ten blocks away. After a while, she is the most successful madam in New York City and buys out her former madam's business as well.
All is well until the police officer sees her and instigates a raid, sending her to jail. Xaviera's attorney bails her out of jail and sets her up with a friend of his who is coming in from Montreal.
Vincent Canby of The New York Times enjoyed the film:
The movie is a cheerily amoral New York comedy about greed and lust in the land of opportunity... Having been derived from such unlikely subject matter, The Happy Hooker is doubley surprising. It's a witty work.
On the other hand, Roger Ebert of the Chicago Sun-Times gave it one star out of four and had this to say:
If Horatio Alger were alive today, he would no doubt be appalled by The Happy Hooker, the story of a girl who gets started off on the right foot in life but, through pluck and endurance, makes bad... What all of this is supposed to prove is beyond me.