Those hospitals include: Regional Medical Center in Palm Springs, Fountain Valley Hospital, John F. Kennedy Memorial Hospital, Lakewood Regional Medical Center, Los Alamitos Medical Center and Placentia Linda Hospital.
The move comes as Health Net says contract negotiations broke down with Tenet over reimbursement rates. But Tenet officials say they were unaware of any such disputes and called the decision "puzzling."
Health Net's Western Region Health Plan President Steve Sell says the company had no choice to drop Tenet's hospitals because Tenet refused requests to negotiate a new contract that more accurately reflects current statewide market conditions.
Health Net officially stopped covering health and medical services at the six hospitals at midnight Dec. 21, when a three-year contract expired.
City News Service contributed to this report.