At the meeting in western Ukraine, Zelenskiy thanked regional allies for keeping trade and transport links open following Russia's full-scale invasion in 2022.
The new grouping - labelled the "Carpathian Eight" - brings together Romania, Serbia, Poland, Slovakia, the Czech Republic, Austria, Hungary and the European Union.
Polish Prime Minister Donald Tusk, Serbian President Aleksandar Vucic and Romanian President Nicusor Dan attended the inaugural event, which is expected to last until Sunday.
"This marks the start of a movement that should bring our countries even closer together and create another strong framework for co-operation at the EU level," Zelenskiy said on Telegram, citing the expansion of energy and logistics co-operation, cross-border trade and security.
"Naturally, security issues are a priority right now and for the years ahead," Zelenskiy said in a speech.
Close to 550 business representatives were expected to attend the forum, with investment and trade agreements worth a billion euro ($A1.6 billion) expected to be signed, Zelenskiy said.
"It's a good start: energy, logistics, infrastructure and cross-sector agreements," he said in a speech broadcast on Ukrainian TV.
Some of the countries attending the meeting, such as Poland and Romania, have been staunch supporters of Ukraine.
Others, such as Hungary, Serbia and Slovakia, have declined to provide direct military assistance to Ukraine.
Meanwhile, Russia's foreign ministry said on Friday it had summoned the United Kingdom chargé d'affaires to strongly protest the UK's continued increase in the supply of drones and other weapons systems to Ukraine.
The ministry said the UK's "fiercely confrontational stance" was aimed at "prolonging and escalating the armed conflict by every possible means".
It added that Russia reserves the right to take necessary countermeasures in self-defence and that "any British military facilities in Ukraine used to strike Russian territory represent legitimate targets".
with AP
