The Film and Publication Board has given "The Spear" painting a "16N" rating, it announced on Friday.
It means that children under the age of 16 should not have access to the artwork because it displays nudity.
"The FPB therefore presents to you that a classification rating of '16N' has been decided upon by the classification committee for the artwork by Brett Murray titled 'The Spear'," chairperson Thoko Mpumlwana said during a briefing in Johannesburg.
"Any persons or entities wishing to publish and exhibit images and/or replicas of this specific artwork will in future have to put in place mechanisms to regulate access to this piece of art by members of the public below the age of 16."
FPB CEO Yoliswa Makhasi said the board understood the image of the painting had gone viral, but urged youths to delete copies of it.
"We don't seek to punish people in our day-to-day work," she said.
The board said it would not report people to police, but would work with service providers to limit access to the image.
When asked how this image differed from other nude artworks, FPB chief operations officer Mmapula Fisha said Murray's painting was not just a piece of nude art.
"The artwork has forced society to revisit its painful history."
The classification had to balance this and artistic merit.
Mpumlwana reiterated that the board could not hear a classification complaint against the City Press, only the Press Ombudsman could.
City Press published a photograph of the painting on its website. It removed the image on Monday, following an outcry and calls for a boycott.
Mpumlwana finished by saying that if any of the affected parties were dissatisfied with the decision they could appeal to the FPB's appeals tribunal within 30 days.
The painting, which was vandalised last Tuesday, depicted President Jacob Zuma with his genitals exposed.