Financial returns filed with Elections Manitoba show Ashton raised $44,378 for the March race in which he finished third.
That's $25,000 less than second-place finisher Theresa Oswald.
Selinger, who survived the leadership challenge by a 33-vote margin, has yet to file his financial statements.
The documents also show Ashton spent more money than he raised, leaving him with a $16,746 deficit that he hopes to eliminate by the fall.
Ashton says the campaign faced hurdles, especially the tight time frame between the start of the race in December and the vote in March.
"We had the (Christmas) holidays and that made it a challenge both in terms of the main campaign itself, but certainly in terms of fundraising," Ashton said Tuesday.
"But the timing was what it was and you work around it. That's what we did and I was proud of the campaign we ran."
Ashton's donors included some familiar names. His daughter Niki Ashton, a member of Parliament, was among the biggest, with a total of $2,489. A few provincial caucus members gave money as well, including Jim Maloway, Dave Gaudreau and legislature Speaker Daryl Reid.
The leadership race was sparked by a partial caucus revolt last fall as the NDP continued to sag in opinion polls. Oswald, who was minister of jobs and the economy, and four other senior cabinet members suggested Selinger should consider resigning.
Selinger refused and called for a leadership race that was decided at the party's convention.
Ashton, a longtime minister of infrastructure and emergency measures, was not part of the revolt. It was his second attempt at the leadership — he lost to Selinger in a two-way race in 2009.
This time around, Ashton finished with 30 per cent of the vote on the first ballot and was dropped in the second round.
When asked Tuesday whether he plans to take another swing at the leadership in the future, the 59-year-old would only say it is not on his mind right now.
"After 2009 and 2015, my focus is getting back as minister," said Ashton, who stepped down from cabinet during the race and was reinstated by Selinger in April.
"Going into the (April 2016) election, we're going to be united."
NDP leadership candidates were allowed to spend a maximum of $71,945. Oswald spent $67,121 — $2,608 less than she raised.
Note to readers: This is a corrected story. A previous version said $15,000.