In a pan-governmental meeting Wednesday, Prime Minister Chung Sye-kyun said the stronger measures will take effect this Friday or sooner.
South Korea will require people arriving from the United States to self-isolate if they have no symptoms.
Those who do have symptoms will be tested at the airport and transfered to medical institutions if they test positive.
"Because imported cases are rising, it's very urgent to tighten our quarantine measures on all travelers from the U.S.. Considering the urgency, our target is to start implementing these measures no later than Friday."
Mandatory testing will also apply to people coming for short visits.
The South Korean government decided to take these measures because of a surge in the number of confirmed cases of COVID-19 coming in from other countries.
"51 of the 100 new cases on Tuesday originated from abroad."
According to the Central Disaster Management Headquarters, about 80 percent of the passengers coming in from the U.S. are South Korean citizens.
More of them are deciding to come home from their U.S. schools and jobs as the number of cases in the U.S. and Europe soar.
Tickets to Incheon are in short supply, and the price has skyrocketed.
Seats in economy class on the Korean Air's flight this Sunday from New York are all sold out.
Only business class is available, and those seats cost more than 8,3-hundred U.S. dollars a piece.
About 600 South Korean citizens in Italy are scheduled to return home next week on a plane chartered by the government.
They'll each have to pay about 16-hundred dollars.
South Koreans in Germany are also scrambling to book tickets home, because flights between the two countries will be suspended from April 1st to the 16th.
Eum Ji-young Arirang News.