South Ossetian leader Leonid Tibilov has signed a decree appointing former presidential candidate Alla Dzhioyeva to be deputy prime minister.
Dzhioyeva won November's presidential runoff, but the republic's highest court annulled the results citing unspecified "irregularities" in the voting.
Dzhioyeva, a former education minister who reportedly rankled Moscow, was also prohibited from competing when the elections were held again earlier this year.
Some believe Dzhioyeva was disqualified because the Kremlin supported another candidate.
The eventual winner, Tibilov, is a former local KGB head who has suggested he wants to unite the region with North Ossetia, which is part of Russia.
Russia has recognized South Ossetia as an independent country and has supported authorities there since the republic broke away from Georgia at the end of the brief Russian-Georgian conflict in August 2008.
Based on reporting by ITAR-TASS and Interfax