The judges say Campbell's fears for her safety and privacy are legitimate because of her high profile and the intense media interest in her appearance.
In its ruling, the Special Court for Sierra Leone instructed authorities to ensure that no one photograph, video tape or even sketch Campbell in or around the courtroom.
Her testimony, however, will be recorded as usual by courtroom cameras.
She is due to appear Thursday, but judges have not yet decided on a motion submitted last week by Taylor's lawyers to delay her appearance.
Measures to protect witnesses in war crimes cases are routine, especially when disclosure of their identity could subsequently endanger them or their families. Such witnesses testify under pseudonyms and with their images blurred in recordings of their testimony.
But blocking the media from photographing a known witness is highly unusual.
The court did not go as far as Campbell had wanted. She had asked the judges for a gag order on all information "gleaned about her stay at the court" apart from her public testimony.
Campbell was summoned to testify about whether she received diamonds from Taylor after a celebrity-studded dinner in South Africa in 1997. Taylor is accused of trading in "blood diamonds" in exchange for helping rebel factions during the 11-year civil war in Sierra Leone. He has denied possessing such conflict diamonds.
The court granted Campbell's request to have a lawyer present, but restricted the attorney's intervention to protecting her from possible self-incrimination on the stand.