The ruling followed an urgent request from two senior party members alleging opacity and irregularities in the organisation of the congress, court documents.
The complaints were not directly aimed at Thiam, but the plaintiffs said that a day before the congress, they did not have the names of the shortlisted candidates for the presidency or the names of party members who will be voting.
The court sided with the plaintiffs and ordered the postponement of the congress.
The winner of the contest to lead the Democratic Party, known by its French acronym as the PDCI, stand the chance of being the party’s candidate in the presidential election.
Since leaving Credit Suisse, Thiam, 61, has returned to politics in Ivory Coast, and submitted his candidacy last month to lead the party that ruled the West African nation from independence to the early 2000s.
Thiam’s campaign team said in a statement on Saturday that police had cordoned the hotel in Abidjan where the congress was scheduled to hold.