All's Well, Ends Well 2009 () is a 2009 Hong Kong romantic comedy film directed by Vincent Kok. It is the fourth instalment in the All's Well, Ends Well film series, the previous film being All's Well, Ends Well 1997.
The film stars Louis Koo as a "love therapist" who is hired to woo a hot-tempered young woman (Sandra Ng) by her brother (Ronald Cheng) in the hopes of following a family marriage tradition. Raymond Wong, the producer and co-star of all four films, appears as a private investigator. All's Well, Ends Well 2009 was released in Hong Kong, China, Singapore, and Malaysia on 22 January 2009 and in New Zealand for one week beginning 29 October 2009. As with the last three films, All's Well, Ends Well 2009 was released as a Chinese New Year film, where a film's release is timed to coincide with the larger movie audience at that time of year.
Kei's (Ronald Cheng) eldest sister Yu Chu (Sandra Ng) is a hot-tempered magazine editor and her temperament has left her single all this while. They have a traditional family and one of the rules is that none of the siblings could get married before their eldest sister. In view of this, Kei sort help from the famous "Casanova", Koo Chai (Louis Koo), who is the new journalist in Sandra’s firm to pretend to court his eldest sister and lure her into the mood of love.