The eight patients, whose ages range from 31 to 79 years old, push the total number of infections from Middle East Respiratory Syndrome up to 162, the health ministry said.
No new fatalities have been reported, it added.
The outbreak started on May 20 when a 68-year-old man was diagnosed after returning from a trip to Saudi Arabia.
Since then the virus has spread at an unusually rapid pace, sparking widespread public alarm over what has become the largest outbreak outside Saudi Arabia.
The eight new South Korean cases include four who were infected at Samsung Medical Center in Seoul -- the epicenter of the outbreak where nearly 80 patients, visitors and medical staff have contracted the virus.
A staff member at the hospital is also among the new cases, though the health ministry said it was unclear where the 33-year-old had been infected.
Staff members at two other hospitals were also diagnosed, as well as a patient in the city of Hwaseong.
More than 5,000 people who were directly or indirectly exposed to the patients have been placed under quarantine in state facilities or at home.
There is no vaccine for MERS which has a mortality rate of 35 percent, according to the WHO.
In Saudi Arabia, more than 950 people have been infected and 412 died from the potentially deadly virus.