Pope Francis was greeted by cheers from Chinese Catholics as he arrived for mass at the World Cup Stadium in Daejeon - his first public event following his arrival in Seoul yesterday.
Some 50,000 people gathered at the stadium, about 112 miles (180 km) south of Seoul, with many wearing cardboard hats with the words "Viva Papa" and holding images of the Pope.
As the Pope entered the stadium to conduct the mass on the Solemnity of the Assumption, crowds rose waving white handkerchiefs and shouting "Viva Papa" and "Mansei", which means "long live" in Korean.
Among the crowd were 38 survivors and relatives of victims of the recent ferry tragedy in which 300 people died, most of them schoolchildren.
During the mass, Pope Francis offered a special prayer for the victims and their families and urged Koreans "united in grief" to work together for the common good.
South Korean Catholic, Choi Deok-Ryeol, said, "I was moved. Before I knew it, I was crying when the Pope was patting children's heads. It was really touching."
Thousands without tickets for the mass cheered and waved flags as the Pope rode to the venue in an open-topped car, stopping from time to time to give a personal blessing to young children and infants held up by their parents.
The Pope began his five-day tour of South Korea on Thursday- marking the first papal visit to the Asian nation in 25 years.
During his visit he surprised South Koreans by shunning an expensive luxury car to travel in a compact car instead.