Doctors failed to detect the girl's brain tumour despite extensive tests and treatments carried out at the at the Kalmar County hospital, the local Barometern newspaper reported.
The girl first sought treatment in 2007 for impaired motion and delayed development, leading doctors to diagnose her with ADHD.
In 2011, she began receiving psychiatric care and prescribed medicine. Not long after, she complained of severe headaches and vomiting, which doctors believed were side effects of the medication.
The girl's condition worsened, and in January 2012 she was admitted to the emergency room in Kalmar and later transported more than 200 kilometres to Linköping University Hospital.
She died the following day during an operation which revealed she had been suffering from a haemorrhaging brain tumour.
An internal investigation carried out by the Kalmar County Council revealed no single doctor had a clear, overarching picture of the girl's condition, Barometern reported.
The incident has since been reported to Sweden's National Board of Health and Welfare (Socialstyrelsen) in accordance with Sweden's Lex Maria laws, the informal name for regulations governing the reporting of injuries or incidents in the Swedish health care system.