But his entry into the race came too late for him to be included in the party's first leadership debate set for Saturday.
"We're still completing our paperwork, so I've been told that I will not be able to take part in the debate," Axworthy said Friday.
"I'm disappointed in that because I think an open, democratic party should be able to accommodate those things."
The party's executive director, George Baars-Wilhelm, said Axworthy cannot be considered an official candidate because his nomination paperwork, which must include signatures from Liberals from all regions of the province, was still a work in progress.
Axworthy joins lawyer Rana Bokhari and business owner Dougald Lamont in the contest to replace outgoing Liberal leader Jon Gerrard.
Gerrard is stepping down following a disastrous 2011 election that saw the Liberals reduced to one legislature seat and just 7.5 per cent of the vote.
Axworthy was a late entry in the race. Nominations opened in May and close next Wednesday. Earlier this month, he sent out an email to friends and family members asking for support for his leadership bid.
The Axworthy name runs deep in the Liberal party. Bob's eldest brother, Lloyd, was a longtime federal cabinet minister. Another brother, Tom, was a principle secretary and speech writer to former prime minister Pierre Trudeau.
But Bob Axworthy has not had the same kind of success. He has at times struggled financially and owned a Winnipeg hotel in the 1970's when it went under.
Axworthy surprised many when he finished a strong second in a 2012 byelection in Fort Whyte, a Progressive Conservative stronghold. More recently, Axworthy has been doing non-profit work in Winnipeg's core area.
"In terms of the poverty cycle in the core, I'm very passionate about that ... and I feel we do have to make changes."
The Liberals have scheduled a second debate for Oct. 3. The party will elect a new leader Oct. 26 via a one-member, one-vote system.