It will also direct those who engaged with those posts to information about virus myths debunked by the World Health Organization.
Social media is awash in bad takes about the outbreak and platforms have begun to combat that misinformation.
Facebook said Thursday that people would begin seeing warning messages in the coming weeks.
Facebook and other platforms have already taken steps to curb the wave of dangerous misinformation that has spread along with the coronavirus.
Facebook has banned bogus ads promising coronavirus treatments or cures. No such thing exists. There is no vaccine, though there is a global race to develop one.
The tech giant is altering its algorithms and, through an information page, attempting to put before users facts about the virus from global health organisations, as well as state and local health departments.
That has not stopped the spread of bad information.
Conspiracy theories about the origin of the virus and the vaccines being developed to prevent it still pop up daily.
Posts or videos that promote unverified treatments and cures have raked in thousands of views.
Facebook users, for example, viewed a false claim that the virus is destroyed by chlorine dioxide nearly 200,000 times, estimated a new study out today from Avaaz, a left-leaning advocacy group that tracks and researches online misinformation.
The group found more than 100 pieces of misinformation about the coronavirus on Facebook, viewed millions of times even after the claims had been marked as false or misleading by fact-checkers.
Other false claims were not labelled as misinformation, despite being declared by fact-checkers as false. Facebook partners with news organisations around the world to provide fact checks of misleading content on its site. The Associated Press news agency is part of that fact-checking programme.
“Coronavirus misinformation content mutates and spreads faster than Facebook’s current system can track it,” Avaaz said in its report.
Fake information on social media has been deadly. Last month, Iranian media reported more than 300 people had died and 1,000 were sickened in the country after ingesting methanol, a toxic alcohol rumoured to be a remedy on social media.
An Arizona man also died after taking chloroquine phosphate – a product that some mistake for the anti-malaria drug chloroquine, which President Donald Trump and conservative pundits have touted as a treatment for COVID-19.
Health officials have warned the drug hasn’t been proven safe or effective as a virus therapy. Side effects of chloroquine can be dangerous.