The boost comes amid continued criticism from President Donald Trump, who has frequently slammed allies for not meeting NATO defense spending targets.
Twenty-five NATO allies plan to increase spending in real terms in 2017, according to the report.
Speaking to reporters Thursday, NATO Secretary General Jens Stoltenberg called the new money "a significant increase," adding that "European Allies and Canada spent almost $46 billion more on defense" since 2014.
"We are moving in the right direction when it comes to burden-sharing and defense spending," he added.
It's the first time NATO has published its annual report on member defense spending since Trump was inaugurated.
Trump has made getting America's NATO allies to spend more on defense a central theme of his foreign policy, using an appearance at a summit of alliance leaders in May to scold his fellow leaders
on the need to boost their defense budgets.
"Twenty-three of the 28 member nations are still not paying what they should be paying and what they are supposed to be paying for their defense. This is not fair to the people and taxpayers of the United States," Trump said during his speech in Brussels following last month's summit.
Montenegro has since joined NATO, becoming the alliance's 29th member.
While other US Presidents have complained that other NATO members have not paid their fair share, Trump has made boosting allied defense spending a central plank of his engagement with the transatlantic alliance.
But now for the first time in years, a sixth country, Romania, has joined the ranks of NATO members who spend 2% of their country's GDP on defense. Romania now joins the US, Greece, the UK, Estonia and Poland in meeting that NATO defense spending target.
Several other countries have also made major jumps in defense spending, with Latvia and Lithuania now projected to increase what they spend from about 1.4% of GDP in 2016 to over 1.7% in 2017. Both Baltic nations are expected to reach the 2% target by 2018.
Trump has claimed credit for some of the defense increases, telling reporters at a news conference with the President of Romania earlier this month that "because of our actions, money is starting to pour into NATO."
Trump also commended Romania's president, Klaus Iohannis, for his country's decision to boost defense investment: "We hope our other NATO allies will follow Romania's lead on meeting their financial obligations and paying their fair share for the cost of defense."
"Other countries are starting to realize that it's time to pay up, and they're doing that. Very proud of that fact," Trump added.
Experts see concerns about Russia as the principle driving factor behind increasing defense budgets. The allies unanimously pledged to meet the 2% target by 2024 at the NATO summit in Wales in 2014 shortly after Russia's military invasion of Crimea.
But NATO officials have also credited Trump with drawing attention to the issue.
"I welcome the focus of the President on increased defense spending. At the same time, it's important to understand that this is implementation of a decision we all made together," Stoltenberg said at a news conference Wednesday in advance of Thursday's meeting of alliance defense ministers.
But while spending has increased among many NATO members, the average for non-US NATO members is still just 1.46% of GDP, well below the 2% target. Germany, a frequent target of Trump's criticism, is projected to increase its defense spending by only 0.02% of GDP, going from 1.2% to 1.22%.
NATO members do fare a bit better in another category: spending money on military equipment.
Thirteen members are projected to hit a key NATO target and spend at least 20% of their defense budgets on equipment. An additional four countries will spend at least 19%. Only seven members met this 20% target in 2014.
Military analysts see the 20% target as indicative of whether countries are investing in the right capabilities to give their militaries a competitive edge.
Romania is projected to spend close to 46% of its defense budget in 2017 on equipment, including ships, mobile missile systems, and armored vehicles, a Romanian military official told CNN.
"It is actually very encouraging to see that we are delivering both on spending cash and on capabilities," Stoltenberg said Thursday following the meeting of defense ministers.
The US has also lobbied NATO members to adopt "national plans" that will in part outline how each member plans to reach the 2% target.
Stoltenberg said Wednesday that the first set of reports on national plans will be completed by December, and reviewed by allied defense ministers in February.
He added the reports will "cover cash, contributions to missions and operations; and the capabilities we need."