Die Volksblad reported that Hans Williams, 76, collapsed as he was reading from the Bible.
He had just told the congregation that it was the day on which he and his deceased wife would have celebrated their 50th wedding anniversary.
Williams had retired as a pastor but still regularly led weddings and funerals.
His daughter Lauretta van Wyk said her father had still been in mourning for her mother who died last year.
Community members remembered him as wise, thoughtful and active in the church and his community.
He was survived by two sons, three daughters and 12 grandchildren.