All's Well, Ends Well 2009 (traditional Chinese: 家有囍事2009; Cantonese Yale: Ga Yau Hei Si 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 last film being All's Well, Ends Well 1997.

The film stars Louis Koo as a womanizer 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 and New Zealand on 22 January 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 Sandra (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.

With Sandra falling in love with Koo Chai, she decides to introduce him to her parents (Lee Heung Kam, Ha Chun Chou). However, Koo Chai fell in love with another girl, Mun during an assignment and this broke Sandra’s heart. To avoid the disappointment of her parents, Sandra asks Mr. Wong (Raymond Wong) a private investigator to pretend as her boyfriend.

With Sandra love life going nowhere and her career plunging low, will she get what she wants? Will Kei find his true love and marries her sister off? Who will Koo Chai choose? Will all’s well end’s well?