Duceppe takes over from Mario Beaulieu, who was leader of the Bloc for less than a year.
Duceppe, the former leader of the sovereigntist party, lost his own seat seat in the 2011 election, when his party suffered a massive reversal at the hands of the New Democrats in Quebec.
He promptly resigned as party leader.
On Wednesday, 297 of 300 party members in attendance voted in favour of Duceppe returning to the helm.
Duceppe thanked the party for its support and tried to rally the troops, saying the Bloc is the only party that can properly defend Quebec's interests in Ottawa.
He told reporters not to read too much into the fact the Bloc chose to have its meeting on Canada Day.