The 43-year-old, who previously coached Tunisia's Olympic team and played at the 1998 World Cup, is tasked with securing a berth at the 2012 African Nations Cup finals, being co-hosted by Equatorial Guinea and Gabon.
Trabelsi's appointment was decided at a meeting of the Tunisian Football Federation on Thursday and comes after he led home-based players to success in last month's African Nations Championship in Sudan.
Terms and conditions of the contract were not revealed.
Trabelsi replaces Ammar Souyah, who was appointed last month to replace Faouzi Benzarti but departs without taking charge of a match.
Souyah had been brought back to the job in January but quit in the wake of the popular uprising in the north African country that led to the toppling of the government.
Benzarti later said he had been pressurised into taking the post by then-president Zine al-Abdine Ben Ali.
Tunisia are still in the running to grab one of the two automatic qualification spots from their group but have three crunch matches to come over the next few months.
Trabelsi will debut at the helm of the team when they meet Oman in a friendly in Muscat on March 29.
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