Gieng Thi Mui, 30, of the southern province of Dong Nai, tested positive on Wednesday.
The Foreign Service of Jiangxi said in a notice it sent to the Vietnamese embassy in Beijing that she is now quarantined at a local hospital and is in stable condition, Vietnam News Agency reported.
Mui is married to a Chinese man and lives with him in Jinzhou City in Jiangxi, which is one of 31 provinces and cities in China placed under lockdown to contain the epidemic.
All 31 direct jurisdictions in mainland China have reported cases of infection.
The virus (nCoV) has spread to Hong Kong, Macao, Thailand, Singapore, Taiwan, Malaysia, Japan, Australia, the U.S., South Korea, France, Germany, Canada, Vietnam, the UAE, Nepal, Cambodia, Sri Lanka, India and the Philippines.
Chinese authorities said 213 people have died as of Friday morning out of more than 9,600 confirmed cases of the disease.
The World Health Organization (WHO) has said an animal appears to be the most likely primary source of the virus. China says the virus could have come from a market in Wuhan where wildlife was traded illegally.
WHO declared a global public health emergency on Thursday.
As of Thursday afternoon Vietnam had five cases of infection, three Vietnamese and two Chinese nationals.
The Vietnamese government has deployed various measures to prevent outbreaks, including suspending all flights to and from epidemic-hit areas in China and suspending visas to visitors from those areas.
As of Friday Vietnam had 97 suspected cases with signs of fever and cough. Of them, 32 are in quarantine pending test results.