There were few heated exchanges in the debate, aside from a few notable jabs by party strategist Brian Topp to fellow leadership candidates Paul Dewar and Martin Singh.
Topp himself acknowledged the cordial tone of the debate, held before a few hundred people in a Quebec City hall.
"If there's one thing we learned from the Liberals, it's that we shouldn't have a civil war in our party," Topp told reporters afterward. "We try to not be too mean to each other."
While the focus of the debate was Canada's role in the world, there weren't many clear disagreements over foreign policy as some of the candidates struggled to express themselves in French.
French skills are expected to be an important factor in the leadership race, with the party losing ground in opinion polls in Quebec since grabbing 59 seats in last May's election.
The leadership debate was the first to take place in French, with only a brief segment in English during the 90-minute session.
NDP deputy leader Thomas Mulcair and former party president Brian Topp appeared most comfortable, while Ottawa MP Paul Dewar had trouble at times.
Dewar faced questions from Topp over his decision to appoint fellow NDP MP Charlie Angus, another anglophone, as deputy leader of his campaign.
Toronto MP Peggy Nash also took aim at Dewar over the issue, stressing the party should recognize the support it received from Quebec in the last election.
"It is for him to determine whether (the appointment of Angus) is respectful to Quebec, but I think the diversity of our country is very important," she told reporters afterward.
Dewar shot back at Topp saying he doesn't even have a seat in the House of Commons, and questioned what he would do if he lost in a by-election.
Mulcair, meanwhile, played up his Quebec ties right from the start, recalling his experience as a cabinet minister in the provincial Liberal government before making the jump to federal politics.
With Romeo Saganash dropping out on Friday, there are now seven candidates in the running to succeed Jack Layton.
The other candidates are British Columbia MP Nathan Cullen, businessman Martin Singh, and Manitoba MP Niki Ashton, the youngest candidate in the race, who has a solid grasp of French.
Speaking with reporters, Topp acknowledged the NDP could do more in Quebec, saying the party should have taken a stronger stance when the Conservative government appointed an auditor general who can't speak French.
Topp said the new leader will have to work hard to prove to Quebecers they made the right choice in the last election.
"We will have three years to do the job of four years," he said. "It's tough, but that's the consequence of losing your leader."
This was the third of six debates before a March convention in Toronto, where the party will select Layton's permanent successor.
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