Matthau died of full cardiac arrest in Santa Monica on July 1, 2000, aged 79. After undergoing heart surgery some years before, doctors discovered that he had colon cancer, which, by the time of his death, had spread to his liver, lungs, and brain. However, on his death certificate the causes of death are listed as cardiac arrest and atherosclerotic heart disease, with ESRD and atrial fibrillation added as "other significant conditions contributing to death but not related to [primary] cause..." His remains are interred in the Westwood Village Memorial Park Cemetery in Los Angeles.
Just under one year later, Jack Lemmon's remains were buried at the cemetery next to those of his friend Matthau, after dying from colon cancer and bladder cancer. After Matthau's death, Lemmon as well as other friends and relatives appeared on Larry King Live in an hour of tribute and remembrance; many of those same people appeared on the show one year later, reminiscing about Lemmon.