In addition to attending an EU summit, Zelenskiy will address the European Parliament during his visit to the Belgian capital, the third stop on a European trip.
While the Ukrainian leader is unlikely to secure immediate pledges to satisfy his requests, the visit gives him a chance to make his case in person with the EU's 27 national leaders for the first time since Russia's invasion on February 24 last year.
The trip was only Zelenskiy's second known time out of his country since the war began and followed a surprise visit to Washington in December.
The president started on Wednesday in London, where he won a British pledge to train Ukrainian pilots on advanced NATO fighter jets from British Prime Minister Rishi Sunak.
He then met French President Emmanuel Macron and German Chancellor Olaf Scholz in Paris for talks over dinner.
Both vowed continued support for Ukraine, and Zelenskiy again pressed for advanced arms.
"France and Germany have the potential to be game changers and that's how I see our talks today," Zelenskiy said.
"The sooner we get heavy long-range weapons and our pilots get modern planes ... the quicker this Russian aggression will end."
Zelenskiy similarly stressed his plea for combat aircraft in a speech to British lawmakers when he referred to the planes as "wings for freedom".
At a joint news conference with Zelenskiy, Sunak said "nothing is off the table" when it comes to supplying Ukraine with jets to fight Russia.
Britain's announcement did not commit to providing Kyiv with jets but signalled a shift that could pave the way for other nations to send planes.
Western countries have so far stopped short of offering planes or weapons that can strike deep inside Russia.
The United States, which has refused to send Kyiv F-16 fighter jets, is expected to announce a $US2 billion ($A2.9 billion) weapons package in coming days that would include rockets with bombs that double the range of those it sent last year.
Russia's embassy to Britain warned London against sending fighter jets to Ukraine, saying such a move would have ramifications for the entire world, TASS news agency reported.
On the question of joining the EU, Ukrainian officials are pushing for membership talks within months.
Scholz seemed to nod to Kyiv's concerns in Paris on Wednesday when he said: "I am taking a clear message to Brussels: Ukraine belongs to the European family."
A Ukrainian official said Ukraine was "absolutely sure the decision to start accession negotiations can be taken this year".
While some EU member countries want to give Ukraine the morale boost that would come with membership talks, others are much more cautious.
They have stressed would-be members need to meet a range of criteria - such as cracking down on corruption - before they can even start negotiations.
New sanctions against Russia are also likely to be discussed in Brussels.
Scholz said on Wednesday in Berlin the EU would tighten sanctions against Moscow again on the war's anniversary.
Diplomatic sources told Reuters last month EU countries were working on a 10th package of sanctions that should be ready for February 24.
On the ground in Ukraine, the country's military said Russian attacks remained intense on Wednesday in the eastern Donetsk and Luhansk regions.
Moscow's forces concentrated on the areas of Kupiansk, Lyman, Bakhmut and Aviivka, the General Staff said on Facebook.
Air strikes and shelling also targeted the Sumy, Kharkiv and Zaporizhzhia regions in northern, northeastern and central Ukraine.
Reuters could not independently verify the reports.
After major Ukrainian gains on the ground late last year, Russia has recovered momentum, sending tens of thousands of freshly mobilised troops to the front.
They have made incremental progress in relentless winter battles both sides describe as some of the bloodiest fighting of the war.
