Allan Boesak, one of the most visible figures during the anti-apartheid struggle, was convicted on Wednesday of stealing money donated to fight white rule, including funds from singer Paul Simon.
Boesak was found guilty on four counts of fraud or theft totalling 400-thousand dollars and acquitted on 23 other charges.
Judge John Foxcroft pronounced guilty of one count of fraud and one of theft in the Simon case.
Singer Paul Simon donated two hundred thousand dollars to the Foundation for Peace and Justice charity, headed by Boesak, after a South African concert tour in 1988.
But Boesak only passed one hundred and twenty eight thousand dollars on to charity and Judge Foxcroft ruled that Boesak had used the remainder for his own purposes.
Foxcroft said that part of the problem had been that trustees and donors had been blinded by Boesak's "larger than life personality" and reputation.
He also said Boesak was guilty of the theft of 226-thousand U-S dollars donated by a Swedish government aid agency.
The money was supposed to have gone to make voter-education videos but was used instead to develop a radio studio to be used by his wife, Elna.
Boesak was also found guilty of taking a total of 93-thousand U-S dollars to help buy houses in the upmarket Cape Town suburbs of Vredehoek and Constantia and giving 4-thousand-200 U-S dollars to Elna.
Foxcroft took almost three hours to read through the 27 charges one by one.
Boesak showed little emotion and refused to comment to reporters.
The former head of the World Alliance of Reformed Churches was accused of taking more than 300-thousand U-S dollars for himself and misusing a further 2-point-42 (m) million dollars donated to the Foundation for Peace and Justice charity he headed.
Boesak faces an unspecified fine or jail term - defence lawyer Mike Maritz said no decision had yet been made on an appeal.
Boesak's conviction comes after his bookkeeper Freddie Steenkamp was jailed for six years after embezzling cash from the Foundation.
Once a top African National Congress leader in the Cape Town area, Boesak played a leading role in the anti-apartheid struggle that ended in the country's first all-race elections in 1994.
He gave up an appointment as ambassador to the United Nations in Geneva when the scandal involving his charity emerged.