Jimenez (D-Bergen, Hudson) was tested at Holy Name Hospital on Sunday, and has since been in self-quarantine at home, she said in a statement.
New Jersey had 18,696 confirmed COVID-19 cases including 267 deaths as of Tuesday.
Jimenez's symptoms came on swiftly on Saturday, starting with a pounding headache and body aches.
She contacted her doctor, got tested and results returned Tuesday were positive, she said. Her eighth grade daughter Gianna is showing no symptoms, the assemblywoman said.
"Although I'm still experiencing symptoms such as chest tightness, I remain in good spirit," Jimenez said. "It's tough to keep a mom down."
Jimenez stressed the importance of social distancing.
"Each of us must do our part to help keep our neighbors safe from this serious illness," she said.
"I look forward to working on behalf of the people of New Jersey again as soon as I have recovered."
Click here to follow Daily Voice Jersey City and receive free news updates.