Members of a historic black church worshipped at their sanctuary for the first time since a gunman opened fire at a Bible study meeting, killing nine people.
Police officers stood among the congregation as the service started with a message of love, recovery and healing.
"We still believe that prayer changes things. Can I get a witness?" the Reverend Norvel Goff asked as the congregation responded with a rousing "yes".
"But prayer not only changes things, it changes us," he said.
Sunday morning marked the first service at Emanuel African Methodist Episcopal Church since Dylann Roof, 21, sat among a Bible study group and opened fire after saying that he targeted them because they were black.
Among the nine killed was the church pastor, the Reverend Clementa Pinckney, who was also a state senator.
Events to show solidarity took place throughout the city and beyond. Church bells rang throughout Charleston, which has the nickname of "Holy City" because of the number of churches there.
South Carolina governor Nikki Haley and Charleston mayor Joseph Riley attended the service at Emanuel.
The welcoming spirit Roof exploited before the shooting is still alive, church members said.
"I think just because of what people have gone through emotions are definitely heightened, not just in Charleston but with anyone going to church because it is such a sacred place, it is such a safe place," Shae Erdos, 29, said after a multiracial group of women sang Amazing Grace outside the church on Saturday.
"To have something like that completely shattered by such evil - I think it will be in the back of everyone's heads, really," Mr Erdos said.
Roof had been photographed with the Confederate flag several times before the shooting.