It's been ordered it to pay US$332 million (NZ$572m) in damages.
The verdict includes $7 million in compensatory damages and $325 million in punitive damages awarded to plaintiff Mike Dennis, who was diagnosed at age 51 with a form of non-Hodgkin lymphoma, according to a spokesperson for the company.
The punitive damage award is almost certain to be reduced sharply, as the US Supreme Court has found that punitive damages should be less than 10 times the compensatory damages in virtually all cases.
The jury sided with Bayer on two of four legal claims in the case, the spokesperson said, finding that while the company had failed to warn of Roundup's risks, it had not been negligent and the product was not defectively designed.
The company said in a statement that it has "strong arguments on appeal to get this unfounded verdict overturned and the unconstitutionally excessive damage award eliminated or reduced, given that there were significant and reversible legal and evidentiary errors made during this trial."
A lawyer for Dennis did not immediately respond to a request for comment.
This marks the third trial loss for Bayer this month, after being hit by a $175 million verdict and a $1.25 million verdict in two separate Roundup trials. Before that, it had won nine consecutive trials over similar claims.
Roundup-related lawsuits have dogged Bayer since it acquired the brand as part of its $63 billion purchase of Monsanto in 2018. The company settled most Roundup claims against it in 2020 for up to $10.9 billion, but still faces close to 40,000 Roundup-related cases.
