The decision opens the gates for wider dissemination of pornography in Africa's largest economy, where regulators have previously rejected bids, saying such broadcasts could offend a morally conservative public.
The Independent Communications Authority of South Africa (ICASA) said channels Playboy TV, Desire TV and Private Spice would likely be on the air within six months.
"It is the authority's view that indeed there is no basis or law for the rejection of TopTV's application," ICASA spokesman Paseka Maleka said in a statement.
A previous bid by TopTV last year was turned down. This time, its management cited constitutional guarantees of freedom of expression and choice, arguing that programmes would not breach the law on hate speech or incitement to violence nor would they demean women or children.
Maleka said the sexually explicit channels would be accessible from 8 p.m. to 5 a.m., and TopTV needed to ensure security measures, including a double pin code, were in place to protect children.
TopTV, owned by On Digital Media and whose shareholders include Luxembourg-based telecoms operator SES Astra, was not available immediately for comment.