On Sunday 10 June 2001, Leila was found dead in her room in the Leonard Hotel in London 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.