Ritter's wife Amy Yasbeck and his four children, including actor Jason Ritter, filed the wrongful death suit in Los Angeles County Superior Court on Sept. 3.
The suit said Ritter died in September 2003 of a tear in his aorta. But when he went to the emergency room complaining of chest pain, nausea and vomiting, he was misdiagnosed as having a heart attack, the suit alleges.
The legal action was reported by the entertainment news show "Extra." It also names the medical staff of Providence St. Joseph's Medical Center.
The family alleged the hospital and medical staff were negligent and careless in their examination, diagnosis and treatment of Ritter's symptoms. The suit requests unspecified damages.
The hospital said in a prepared statement that it had not yet seen the suit and could not comment. The hospital also said it would not release information about Ritter because of patient privacy.
Ritter came to prominence in 1977 as Jack Tripper on the hit sitcom "Three's Company." He made a successful return to sitcoms in 2002 with "8 Simple Rules for Dating My Teenage Daughter."