The party of Rached Ghannouchi won 52 of 217 seats in Sunday's election, well short of the 109 needed to govern.
Ghannouchi, a divisive figure, has led Ennahdha for a long time. But until now, he had never run for office.
Late on Wednesday, the election commission announced Ghannouchi won a seat in Tunis.
The recently formed Qalb Tounes party of business tycoon and presidential candidate Nabil Karoui placed second with 38 seats.
Karoui was freed from jail earlier on Wednesday after the Court of Cassation dropped the detention order against him that had kept him behind bars in a money laundering probe since August.
Up until now Karoui has had to campaign for the presidency by proxy - through his wife and on television.
Karoui's release came just days ahead of Sunday's final presidential runoff vote that he will contest against a rival political newcomer, conservative law professor Kais Saied.
In the run-up to the parliamentary vote, Ennahdha and Qalb Tounes had officially ruled out forming an alliance.
And with a plethora of parties and movements, the stage looks set for complex and rowdy negotiations.
The social-democratic Attayar party of human rights activist Mohamed Abbou obtained 22 seats, while Islamist populist lawyer Seifeddine Makhlouf's Karama party secured 21.
Meanwhile, the Free Destourian party of staunchly anti-Islamist Abir Mouss reaped 17 seats, with the female leader also elected Tunis MP.
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