Ennahda and the mainly secular opposition agreed on Saturday to start work on forming a new government along with a special body to oversee elections.
Despite delays due to some last-minute disputes, Ennahda leader Rached Ghannouchi signed the roadmap in the presence of politicians and the media. Ghannouchi had, in a Twitter message, blamed the opposition for "last-minute blackmail" and refused to sign the text.
A deal was eventually reached, although it was initially unclear how the issues were resolved. The terms outline a timetable of three weeks for the creation of a transitional government of independent experts.
"I am optimistic for the future of Tunisia and that the dialogue process will lead to free and transparent elections," said President Moncef Marzouki at the signing ceremony. "The eyes of Tunisians and our friends abroad are on us and we cannot disappoint them - it is an historic responsibility."
The deal, brokered by the UGTT trade union confederation, requires the Ennahda-dominated elected assembly to finish writing a new constitution that would pave the way for elections.
Four mediators drew up the agreement, which provides for the nomination of an independent prime minister by the end of next week.
Ennahda was pressed to relinquish power after the murder of two political opponents sparked accusations that it was doing to little to reign in extremist supporters. In addition, the political turmoil has weakened the country's already fragile economy.
The party was voted into power after the overthrow of the country's deposed authoritarian president, Zine El Abidine Ben Ali, in January 2011.
rc/jr (AFP, dpa)