Hannibal TV, owned by Tunisian businessman Larbi Nasra, made an uncontroversial start at 5pm (1600 GMT) with the reading of verses from the Quran followed by a message from Tunisian President Zain al-Abidin bin Ali.
The president said he wanted to ensure that "liberty of expression is the fundamental rule in development of the Tunisian approach to information".
He pointed to various laws and training mechanisms put in place so that "information is a source of innovation and enrichment for the evolving political culture".
However, during national elections in October 2004, the Danish-based International Media Support watchdog found bin Ali had enjoyed overwhelming exposure during the campaign leading up to the vote while opposition parties had been largely ignored.
Last May, the US State Department also criticised Tunisia's lack of media freedom, listing it with Ukraine as countries in which journalists were subjected to "censorship, harassment" and citing "the authorities' failure to investigate attacks on the media".
The Tunisian government responded by saying media freedoms in Tunisia had improved, citing the lifting of blocks on certain websites and the creation of private media outlets.
It also denied that it had refused to investigate attacks on the press.
Hannibal TV will be competing with two government channels and follows a government decision in November 2003 to open the audiovisual sector to competition.
The new channel will broadcast in Tunisian with a varied programming targeting the youth market and featuring musical variety shows, series, films and sport.
The first private radio station, Radio Mosaic, began operating immediately after the government decision and has been a success with its largely music format.