Just last week, Carney signed an order to extend the face-covering requirement for students and staff until March 31.
Janice Lorrah, of Hockessin, claims this extension is unlawful.
She says the issue is not about masks being good or bad, but about how the governor went about extending the mandate.
"I'd like to see citizens of Delaware have notice and the opportunity to be heard before having to have such regulations imposed on them," said Lorrah.
She says she has a 6-year-old who is in first grade and doesn't know life at school without masks.
A hearing is set to take place on February 28.
The governor's office declined to comment on the lawsuit.