When the film was originally cast, Natalie Portman was unsuccessful because of her young age. She did not give up, and when she returned to Luc Besson again, she performed a performance, and Natalie Portman finally got the role of Matilda. This is also her debut film.
In filming a scene where Leon and Matilda perform tasks for Tony, director Luc Besson also played a small role, one of the many shooting guys in the background.
During the filming of many police cars parked on the street, a man who had just robbed a store happened to ran out of the store. When he ran into the film crew and numerous "policemen", he chose to surrender to the group of extras in uniforms.
Liv Tyler was considered for the role of Matilda, but she gave up because she was too tall.
The pistol used by Leon in the film is the Beretta 92 series with a silencer.
The original script contains a lot of "sex-related scenes" between Leon and Matilda, including a scene where the two are lying in bed and Matilda talks about sex. These scenes were deleted when they were released in the United States, and can be found in deleted clips of the European version and special edition DVDs.
The pot in the film was cultivated by Leon, and the plant finally replanted by Matilda was Dieffenbachia. The middle part of the word is pronounced "Leon."
