Prime Minister Stephen Harper announced the military contribution, which included the dispatch of up to 20 staff officers to bolster the Canadian presence at NATO headquarters.
NATO requested Canadian participation, the prime minister said.
"This is in response to the situation that is developing there and frankly more generally to the concern that we have on what really is expansionism and militarism on the part of Russia under the presidency of Mr. (Vladimir) Putin," Harper said.
"I believe this to be a long-term, serious threat to global peace and security and we're always prepared to work with our allies in NATO and elsewhere."
At the same time, an intense round of diplomacy in Geveva has produced a tentative agreement that puts on hold — at least temporarily — additional economic sanctions the West had prepared to impose on Russia if the talks were fruitless.
It's unclear where the fighters will be based.
It was earlier reported early Thursday that the jets and their ground support staff will be based in Lask, Poland, where the U.S. is planning a major military exercise later this year. The air base, located southwest of Warsaw, is central and would allow the fighters to participate in a variety of missions.
But a senior government official, speaking on background, said the decision on basing was not final and that NATO planning was still underway.
The government also did not say whether the CF-18s will join beefed-up patrols over the Baltic Sea, which are meant to reassure countries such as Estonia and Lithuania, or whether they will be flying along Poland's border with Ukraine.
It is an important distinction, given the tensions in the region and the sporadic violence that has gripped the Ukraine-Russia border region.
Those decisions will be made as military planners in Belgium get further information.
The Canadian fighter jets will join warplanes from the United States, Britain, Denmark, Poland, Portugal and Germany, which will deploy in waves between now and the fall.
Harper did not say how long the Canadian deployment will last, or whether he will consult Parliament.
Although not bound by legislation, the Conservatives have made it a practice to ask for a vote in the House of Commons when military forces are placed in harm's way.
The last time CF-18s were sent overseas in response to a NATO request was for the 2011 Libya bombing campaign. The question was put to MPs on that mission and on proposed extensions to the Kandahar campaign in Afghanistan.
Harper did not consult Parliament on the recently concluded Afghan training mission, nor the 2013 transport aircraft sent to support French forces battling Islamic insurgents in Mali.
Canada's air force has taken part in patrols over the Baltic and Iceland as part of its regular NATO duties and for that reason defence expert Steve Saideman said he doesn't think the prime minister would have to go to Parliament this time. However, MPs should be consulted as the mission evolves, he added.
The absence of legislated democratic input is unsettling, especially in this day and age, said Saideman.
The British have been much more clear on Parliament's role in overseeing both deployments and continuing operations, something that has helped prevent missions from becoming political circuses, he added.
"Canada just has a tendency to not confront these challenges for a variety of reasons, but this kind of stuff — they just don't want to face it," he said.
Liberal MP Marc Garneau tweeted that his party supports the government's decision to send jets.
On Wednesday, Anders Fogh Rasmussen, NATO's secretary general, announced what was called a "reassurance package" for jittery east European members of the alliance.
Over the next few months additional air, sea and land forces will take up positions in former East Bloc countries.
Canada is also slated to take part in July in a long-planned, U.S.-led military exercise in Ukraine, known as Rapid Trident 2014, but the government has not detailed the size and scope of the country's involvement.
Another defence expert recently questioned the Canadian military's ability to mount sustained operations in eastern Europe or deploy follow-on forces, given that budget cuts at National Defence have taken a bite out of readiness.
Retired colonel George Petrolekas, speaking for the Conference of Defence Associations Institute, told the Commons defence committee that recent "cuts by stealth" have shown the Forces can no longer afford certain things or even maintain some of the things it has.
"Therefore when we come into issues such as the Ukraine, we now start scrambling for solutions because we just don't have forces that are ready to go," he testified last week.
Also on HuffPost