A 73-year-old Saudi woman, infected by the virus and who had suffered chronic illnesses, died in Riyadh, the health ministry said in a statement on its website.
It also reported a new infection of a 65-year-old Saudi man in the northern Al-Jawf province, currently receiving treatment at a Riyadh hospital.
The World Health Organisation says it has been informed of 155 laboratory-confirmed MERS cases worldwide so far, including 64 deaths, most of them in Saudi Arabia.
Experts are struggling to understand the disease, for which there is no vaccine.
It is considered a deadlier but less-transmissible cousin of the SARS virus that erupted in Asia in 2003 and infected 8,273 people, nine percent of whom died.
Like SARS, MERS appears to cause a lung infection, with patients suffering from a temperature, coughing and breathing difficulties.
But it differs in that it also causes rapid kidney failure, and the extremely high death rate has caused serious concern.
In August, researchers pointed to Arabian camels as possible hosts of the virus.
And the Saudi government said on November 11 that a camel in the kingdom had tested positive for MERS, the first case of an animal infected with the coronavirus.