Tsvangirai was released shortly after but his documents were not returned to him, his spokesman George Sibotshiwe said.
Tsvangirai had been invited by South Africa to attend a Southern African Development Community summit of heads of state in Johannesburg starting Saturday.
Talks between Tsvangirai and Zimbabwean President Robert Mugabe on a powersharing government broke down earlier this week after the two men failed to agree on who should be head of government.