Harris painted the work in the Theatre Royal Plymouth in 1994 when he starred in Jack and the Beanstalk.
A spokesman said it was "currently protected by Perspex" but would be "covered in vinyl to obscure it".
The entertainer was jailed for five years and nine months after he was found guilty of indecently assaulting four girls.
A theatre spokeswoman said the mural was in dressing room G4 and would be covered "in the near future".
Harris, 84, was convicted of offences that took place between 1968 and 1986 against the girls who were aged seven or eight to 19.
A mural by disgraced entertainer Rolf Harris, which stands in a theatre dressing room, is to be covered up.