Afriforum was fined for putting up "Mugabe, go home!" posters on lamp posts at the Union Buildings in Pretoria, the organisation said.
Shortly after putting up the posters, Tshwane metro police removed them and issued a fine to the organisation's CEO Kallie Kriel.
"The poster-campaign was initiated as a protest against the fact that the human rights violator, Robert Mugabe, has been invited to this inauguration," Kriel said in a statement.
He said he would oppose the fine in court on 22 June.
"It is a bitter irony that a violator of human rights like Robert Mugabe is welcomed into South Africa with open arms, while those who initiate a peaceful protest against it are prosecuted.
"If anyone is to be prosecuted, it should be Mugabe," Kriel said.
Jacob Zuma will be inaugurated as South Africa's third democratically elected president on Saturday at the Union Buildings.
Sapa
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