On May 13, 2018, Kidder died in her home in Livingston, Montana. She was 69. At the time, her manager, Camilla Fluxman Pines, reported that she passed peacefully in her sleep. She left behind her 41-year-old daughter, Maggie McGuane, whom she had with her ex-husband Thomas McGuane.
Come August of the same year, it was confirmed that Kidder died by suicide. She reportedly died "as a result of a self-inflicted drug and alcohol overdose," according to the deputy coroner. Maggie announced: "It's a big relief that the truth is out there. It's important to be open and honest so there's not a cloud of shame in dealing with this."