Pahlavi never married and spent most of her time commuting between her home in Greenwich, Connecticut, and Paris, where her mother lives. A onetime model for the designer Valentino, she suffered from anorexia nervosa, chronic low self-esteem, severe depression and chronic fatigue syndrome. She spent much of her time being treated in clinics in the United States and Britain. The princess is reported to have spent much of her last year staying at the Leonard Hotel in London paying £450 a night for her favourite suite. The hotel's manager, Angela Stoppani, is quoted in The Daily Telegraph as saying the princess went to the hotel to "chill out".
On Sunday 10 June 2001, Leila was found dead in her room in the Leonard Hotel just before 1930 BST by her doctor. She was found to have more than five times the lethal dose of Seconal, a barbiturate, which is used to treat insomnia, in her system, along with a nonlethal amount of cocaine. She was found in bed, her body emaciated by years of anorexia, bulimia, and food intolerances. According to a report on her death, which included information from an autopsy conducted by the Westminster Coroner's Court, she stole the Seconal from her doctor's desk during an appointment and was addicted to the drug, typically taking 40 pills at once, rather than the prescribed two.
On 17 June 2001, she was buried near her maternal grandmother, Farideh Ghotbi Diba, in the Cimetière de Passy, Paris, France. At the funeral was her mother, the former queen Farah, as well as members of the former French royal family and Frederic Mitterrand, the nephew of the late French President François Mitterrand.
On 4 January 2011, her brother Ali-Reza Pahlavi was found dead at his home in Boston, Massachusetts from an apparent suicide.