The conclusion followed an assessment of 55 hospitals and other healthcare facilities, half of which deemed dysfunctional by the global health body.
The WHO also warned that the safety guidelines for COVID-19 coronavirus were not adhered to in some of the healthcare sites it had inspected.
After a deadly blast ravaged the city of Beirut last week, at least three hospitals were forced to suspend operations over the structural damage caused by the blast.
Another three hospitals had to cut their capacity, the BBC reports.
Last Tuesday, a powerful explosion ripped through Beirut as some 2,750 tons of ammonium nitrate, an explosive chemical substance.
The blast left at least 200 people dead and 6,000 more wounded; hundreds of thousands were rendered homeless as the blast damaged dozens of buildings.
According to Lebanese authorities, restoring Beirut would come with a price tag of $15 billion -- a heavy toll for a country ravaged by a long-running economic crisis.