He showed no emotion as the verdict was read.
Roof, who is white, was accused of fatally shooting nine black parishioners during a Bible study at the predominantly black Emanuel AME Church on June 17, 2015. According to the federal indictment against him, Roof, 22, entered the church armed and "with the intent of killing African-Americans engaged in the exercise of their religious beliefs."
The 33 federal counts against Roof included hate crimes resulting in death and obstruction of exercise of religion resulting in death.
The trial next moves into the sentencing phase, in which the same jury will determine whether Roof will be sentenced to death or life in prison. That will begin on Jan. 3.
After the reading of the verdict, the judge explained to Roof the gravity of the sentencing phase, asking him whether he wants to reconsider representing himself during that phase.
Roof told the judge that he understood and that he plans to represent himself in the sentencing phase. The judge said that he will give Roof until Jan. 3 to reconsider but that once the sentencing phase begins, the decision to represent himself will hold.
In a statement, South Carolina Gov. Nikki Haley said, "It is my hope that the survivors, the families and the people of South Carolina can find some peace in the fact that justice has been served."
Roof also faces a state trial, set for early next year, in which he may also face the death penalty.